Yep sounds faulty stick- its drawing too much power so leave that stick out. Also its your computer dusty inside?
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Also make sure you install them in different positions.
		
		
	 
Update: Just got another kernel panic while I was away (and let the mac turned on...) 
Anonymous UUID:       AD591DAB-1A91-6052-C5B8-25E53A5A965C
Thu Mar 12 20:11:59 2015
*** Panic Report ***
Machine-check capabilities: 0x0000000000000806
 family: 6 model: 15 stepping: 11 microcode: 188
 signature: 0x6fb
 Intel(R) Xeon(R) CPU           X5355  @ 2.66GHz
 6 error-reporting banks
Processor 0: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200001084200e0f
Processor 1: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200001080200e0f
Processor 2: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200000084200e0f
Processor 3: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200000080200e0f
Processor 4: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200001084200e0f
Processor 5: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200001080200e0f
Processor 6: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200000084200e0f
Processor 7: IA32_MCG_STATUS: 0x0000000000000005
 IA32_MC5_STATUS(0x415): 0xb200000080200e0f
panic(cpu 0 caller 0xffffff800fc1ae0a): "Machine Check at 0xffffff7f91961ad4, registers:\n" "CR0: 0x000000008001003b, CR2: 0x000000010bb45000, CR3: 0x000000001307e000, CR4: 0x0000000000002660\n" "RAX: 0x0000000000000008, RBX: 0xffffff80233d6000, RCX: 0xffffff80e0e7200a, RDX: 0x0000000000000008\n" "RSP: 0xffffff811905bba0, RBP: 0xffffff811905bbb0, RSI: 0x000000000000000a, RDI: 0xffffff811905bc68\n" "R8:  0x000000000000000a, R9:  0x0000000000000008, R10: 0xffffff80233d0008, R11: 0x0000000000000000\n" "R12: 0xffffff812c8d0000, R13: 0x0000000000000003, R14: 0xffffff812c8d0000, R15: 0x0000000000000004\n" "RFL: 0x0000000000000286, RIP: 0xffffff7f91961ad4, CS:  0x0000000000000008, SS:  0x0000000000000010\n" "Error code: 0x0000000000000000\n"@/SourceCache/xnu/xnu-2782.10.73/osfmk/i386/trap_native.c:168
Backtrace (CPU 0), Frame : Return Address
0xffffff80f175acf0 : 0xffffff800fb2fe41 
0xffffff80f175ad70 : 0xffffff800fc1ae0a 
0xffffff80f175aed0 : 0xffffff800fc36f2f 
0xffffff811905bbb0 : 0xffffff7f91961e49 
0xffffff811905bbf0 : 0xffffff7f91961ea2 
0xffffff811905bc20 : 0xffffff7f91f7109d 
0xffffff811905bc80 : 0xffffff7f91f70409 
0xffffff811905bcd0 : 0xffffff7f91f70210 
0xffffff811905bdf0 : 0xffffff7f90bb8d6c 
0xffffff811905be40 : 0xffffff7f908731e9 
0xffffff811905be80 : 0xffffff7f90875513 
0xffffff811905bea0 : 0xffffff80100d9d03 
0xffffff811905bf00 : 0xffffff800fb624f9 
0xffffff811905bfb0 : 0xffffff800fc14dd7 
      Kernel Extensions in backtrace:
         com.apple.iokit.IOHIDFamily(2.0)[FD3D361D-51FF-37DC-9A7D-840DFD57DB50]@0xffffff7f90851000->0xffffff7f908c6fff
            dependency: com.apple.driver.AppleFDEKeyStore(28.30)[3BAA7FEE-7EF3-3A9A-A0B1-902A4AB7171F]@0xffffff7f90846000
         com.apple.iokit.IOGraphicsFamily(2.4.1)[619F6C9F-0461-3BA1-A75F-53BB0F87ACD3]@0xffffff7f90bac000->0xffffff7f90be6fff
            dependency: com.apple.iokit.IOPCIFamily(2.9)[56AD16B5-4F29-3F74-93E7-D492B3966DE2]@0xffffff7f90324000
         com.apple.kext.AMDSupport(1.3)[F69B43AA-4529-3560-8643-66579222A749]@0xffffff7f9194e000->0xffffff7f91a6cfff
            dependency: com.apple.iokit.IOACPIFamily(1.4)[70E2B65E-A91A-3522-A1A0-79FD63EABB4C]@0xffffff7f90b3a000
            dependency: com.apple.iokit.IOPCIFamily(2.9)[56AD16B5-4F29-3F74-93E7-D492B3966DE2]@0xffffff7f90324000
            dependency: com.apple.iokit.IOGraphicsFamily(2.4.1)[619F6C9F-0461-3BA1-A75F-53BB0F87ACD3]@0xffffff7f90bac000
            dependency: com.apple.AppleGraphicsDeviceControl(3.8.6)[957EB27F-7D07-3C40-91F5-9B54652F06EE]@0xffffff7f91948000
         com.apple.kext.AMDFramebuffer(1.3)[FA8C8429-80E0-3840-AACD-BF6BBE8AFDAC]@0xffffff7f91f6e000->0xffffff7f91f91fff
            dependency: com.apple.iokit.IOACPIFamily(1.4)[70E2B65E-A91A-3522-A1A0-79FD63EABB4C]@0xffffff7f90b3a000
            dependency: com.apple.iokit.IOPCIFamily(2.9)[56AD16B5-4F29-3F74-93E7-D492B3966DE2]@0xffffff7f90324000
            dependency: com.apple.kext.AMDSupport(1.3.0)[F69B43AA-4529-3560-8643-66579222A749]@0xffffff7f9194e000
            dependency: com.apple.iokit.IOGraphicsFamily(2.4.1)[619F6C9F-0461-3BA1-A75F-53BB0F87ACD3]@0xffffff7f90bac000
BSD process name corresponding to current thread: kernel_task
Boot args:  kext-dev-mode=1
Mac OS version:
14C1510
Kernel version:
Darwin Kernel Version 14.1.0: Thu Feb 26 19:26:47 PST 2015; root:xnu-2782.10.73~1/RELEASE_X86_64
Kernel UUID: 270413F7-3B44-3602-894F-AC0D392FCF8E
Kernel slide:     0x000000000f800000
Kernel text base: 0xffffff800fa00000
__HIB  text base: 0xffffff800f900000
System model name: MacPro2,1 (Mac-F4208DC8)
System uptime in nanoseconds: 7574926294751
last loaded kext at 1066170686809: com.apple.filesystems.smbfs	3.0.0 (addr 0xffffff7f924fd000, size 389120)
last unloaded kext at 7443707125221: com.apple.driver.AppleHIDKeyboard	176.2 (addr 0xffffff7f9134d000, size 32768)
loaded kexts:
org.tgwbd.driver.NullCPUPowerManagement	1.0.0d2
com.apple.filesystems.smbfs	3.0.0
com.apple.driver.AppleBluetoothMultitouch	85.3
com.apple.iokit.IOBluetoothSerialManager	4.3.2f6
com.apple.filesystems.autofs	3.0
com.apple.driver.AppleOSXWatchdog	1
com.apple.driver.AppleUpstreamUserClient	3.6.1
com.apple.driver.AppleMCCSControl	1.2.11
com.apple.kext.AMDFramebuffer	1.3.0
com.apple.iokit.IOUserEthernet	1.0.1
com.apple.driver.AppleHDA	269.25
com.apple.AMDRadeonX3000	1.3.0
com.apple.Dont_Steal_Mac_OS_X	7.0.0
com.apple.driver.AppleLPC	1.7.3
com.apple.driver.AppleHWAccess	1
com.apple.driver.AppleHV	1
com.apple.driver.AudioAUUC	1.70
com.apple.driver.AppleMCEDriver	1.1.9
com.apple.kext.AMD5000Controller	1.3.0
com.apple.driver.ACPI_SMC_PlatformPlugin	1.0.0
com.apple.iokit.SCSITaskUserClient	3.7.3
com.apple.driver.XsanFilter	404
com.apple.AppleFSCompression.AppleFSCompressionTypeDataless	1.0.0d1
com.apple.AppleFSCompression.AppleFSCompressionTypeZlib	1.0.0d1
com.apple.BootCache	35
com.apple.iokit.IOAHCIBlockStorage	2.7.0
com.apple.driver.AppleUSBHub	705.4.2
com.apple.driver.AppleIntel8254XEthernet	3.1.4b1
com.apple.driver.AppleFWOHCI	5.5.2
com.apple.driver.AirPort.Atheros40	700.74.5
com.apple.driver.AppleIntelPIIXATA	2.5.1
com.apple.driver.AppleUSBEHCI	705.4.14
com.apple.driver.AppleAHCIPort	3.1.0
com.apple.driver.AppleUSBUHCI	656.4.1
com.apple.driver.AppleACPIButtons	3.1
com.apple.driver.AppleRTC	2.0
com.apple.driver.AppleHPET	1.8
com.apple.driver.AppleSMBIOS	2.1
com.apple.driver.AppleACPIEC	3.1
com.apple.driver.AppleAPIC	1.7
com.apple.nke.applicationfirewall	161
com.apple.security.quarantine	3
com.apple.security.TMSafetyNet	8
com.apple.driver.AppleIntelCPUPowerManagement	218.0.0
com.apple.driver.IOBluetoothHIDDriver	4.3.2f6
com.apple.driver.AppleMultitouchDriver	262.33.1
com.apple.iokit.IOSerialFamily	11
com.apple.kext.triggers	1.0
com.apple.driver.AppleSMBusController	1.0.13d1
com.apple.driver.DspFuncLib	269.25
com.apple.kext.OSvKernDSPLib	1.15
com.apple.iokit.IONDRVSupport	2.4.1
com.apple.iokit.IOSurface	97
com.apple.iokit.IOAcceleratorFamily2	156.6.1
com.apple.iokit.IOFireWireIP	2.2.6
com.apple.iokit.IOBluetoothHostControllerUSBTransport	4.3.2f6
com.apple.iokit.IOBluetoothFamily	4.3.2f6
com.apple.driver.AppleHDAController	269.25
com.apple.iokit.IOHDAFamily	269.25
com.apple.iokit.IOUSBUserClient	705.4.0
com.apple.kext.AMDSupport	1.3.0
com.apple.AppleGraphicsDeviceControl	3.8.6
com.apple.iokit.IOGraphicsFamily	2.4.1
com.apple.driver.AppleSMC	3.1.9
com.apple.driver.IOPlatformPluginLegacy	1.0.0
com.apple.driver.IOPlatformPluginFamily	5.8.1d38
com.apple.driver.AppleUSBAudio	295.23
com.apple.iokit.IOAudioFamily	203.3
com.apple.vecLib.kext	1.2.0
com.apple.iokit.IOUSBHIDDriver	705.4.0
com.apple.driver.AppleUSBComposite	705.4.9
com.apple.iokit.IOSCSIMultimediaCommandsDevice	3.7.3
com.apple.iokit.IOBDStorageFamily	1.7
com.apple.iokit.IODVDStorageFamily	1.7.1
com.apple.iokit.IOCDStorageFamily	1.7.1
com.apple.iokit.IOATAPIProtocolTransport	3.5.0
com.apple.iokit.IOSCSIArchitectureModelFamily	3.7.3
com.apple.iokit.IOFireWireFamily	4.5.6
com.apple.iokit.IO80211Family	710.55
com.apple.iokit.IONetworkingFamily	3.2
com.apple.iokit.IOATAFamily	2.5.3
com.apple.iokit.IOAHCIFamily	2.7.5
com.apple.iokit.IOUSBFamily	710.4.14
com.apple.driver.AppleEFINVRAM	2.0
com.apple.iokit.IOHIDFamily	2.0.0
com.apple.driver.AppleEFIRuntime	2.0
com.apple.iokit.IOSMBusFamily	1.1
com.apple.security.sandbox	300.0
com.apple.kext.AppleMatch	1.0.0d1
com.apple.driver.AppleKeyStore	2
com.apple.driver.AppleMobileFileIntegrity	1.0.5
com.apple.driver.AppleCredentialManager	1.0
com.apple.driver.DiskImages	396
com.apple.iokit.IOStorageFamily	2.0
com.apple.iokit.IOReportFamily	31
com.apple.driver.AppleFDEKeyStore	28.30
com.apple.driver.AppleACPIPlatform	3.1
com.apple.iokit.IOPCIFamily	2.9
com.apple.iokit.IOACPIFamily	1.4
com.apple.kec.corecrypto	1.0
com.apple.kec.Libm	1
com.apple.kec.pthread	1
Model: MacPro2,1, BootROM MP21.007F.B06, 8 processors, Quad-Core Intel Xeon, 2.66 GHz, 8 GB, SMC 1.7f10
Graphics: ATI Radeon HD 5770, ATI Radeon HD 5770, PCIe, 1024 MB
Memory Module: DIMM Riser A/DIMM 1, 2 GB, DDR2 FB-DIMM, 667 MHz, 0x8551, 0x373254323536393230484644335342202020
Memory Module: DIMM Riser A/DIMM 2, 2 GB, DDR2 FB-DIMM, 667 MHz, 0x8551, 0x373254323536343230454641335342322020
Memory Module: DIMM Riser B/DIMM 1, 2 GB, DDR2 FB-DIMM, 667 MHz, 0x80CE, 0x4D3339355435373530435A342D4345363120
Memory Module: DIMM Riser B/DIMM 2, 2 GB, DDR2 FB-DIMM, 667 MHz, 0x80CE, 0x4D3339355435373530435A342D4345363120
AirPort: spairport_wireless_card_type_airport_extreme (0x168C, 0x87), Atheros 5416: 4.0.74.0-P2P
Bluetooth: Version 4.3.2f6 15235, 3 services, 26 devices, 1 incoming serial ports
Network Service: Wi-Fi, AirPort, en3
PCI Card: ATI Radeon HD 5770, Display Controller, Slot-1
PCI Card: ATI Radeon HD 5770, ATY,VervetParent, Slot-1
Serial ATA Device: KINGSTON SV300S37A60G, 60,02 GB
Serial ATA Device: WDC WD10EVVS-63M5B0, 1 TB
Parallel ATA Device: OPTIARC DVD RW AD-7170A
USB Device: Microsoft LifeCam VX-800
USB Device: DBT-122
USB Device: Wireless Receiver
FireWire Device: built-in_hub, Up to 800 Mb/sec
Thunderbolt Bus: 
Is there still a problem with my RAM, or is it now something else? ...