Upgrading to Mac OS X 10.5; constantly crashing

[ShadowX22]

I've recently upgraded an iMac to OS X 10.5 and ever since then I've been experiencing a problem where OS X will stop responding the screen will grey over from top to bottom and give me an message that I need to restart my computer. When I restart and I log back in, there's this error message, from the problem detail:

Interval Since Last Panic Report: 150 sec
Panics Since Last Report: 2
Anonymous UUID: 20B1C043-29D3-41C6-A176-14899C408DC5

Fri Sep 25 13:42:39 2009
panic(cpu 0 caller 0x001AB0FE): Kernel trap at 0x0022afe6, type 14=page fault, registers:
CR0: 0x8001003b, CR2: 0x00000088, CR3: 0x010f4000, CR4: 0x000006e0
EAX: 0x00000000, EBX: 0x00136817, ECX: 0x00000002, EDX: 0x00000044
CR2: 0x00000088, EBP: 0x20f9fe50, ESI: 0x037b07d8, EDI: 0x20e8bbb4
EFL: 0x00010206, EIP: 0x0022afe6, CS: 0x00000004, DS: 0x0309000c
Error code: 0x00000000

Backtrace (CPU 0), Frame : Return Address (4 potential args on stack)
0x20f9fcb8 : 0x12b4c6 (0x45f91c 0x20f9fcec 0x13355c 0x0)
0x20f9fd08 : 0x1ab0fe (0x469a98 0x22afe6 0xe 0x469248)
0x20f9fde8 : 0x1a1713 (0x20f9fe08 0x216e57 0x2a9a640 0x37574a4)
0x20f9fe00 : 0x22afe6 (0xe 0x3270048 0x20f9000c 0x22000c)
0x20f9fe50 : 0x35952f2c (0x44 0x20f9fe94 0x2 0x36d7900)
0x20f9ff3c : 0x358fd1b6 (0x1 0x35987070 0x0 0x1417c7)
0x20f9ffac : 0x359681e2 (0x359810f0 0x35968018 0x3450000 0x20e8bbb4)
0x20f9ffc8 : 0x1a14fc (0x20e8bbb4 0x0 0x1a40b5 0x3632f20)
Backtrace terminated-invalid frame pointer 0
Kernel loadable modules in backtrace (with dependencies):
org.openafs.filesystems.afs(1.3.82)@0x358f1000->0x3598efff

BSD process name corresponding to current thread: kernel_task

Mac OS version:
9L31a

Kernel version:
Darwin Kernel Version 9.8.0: Wed Jul 15 16:55:01 PDT 2009; root:xnu-1228.15.4~1/RELEASE_I386
System model name: iMac4,1 (Mac-F42786C8)

System uptime in nanoseconds: 1283486341097
unloaded kexts:
com.apple.driver.InternalModemSupport 2.4.0 - last unloaded 90149246264
loaded kexts:
com.Symantec.kext.SymAPComm 10.1.0 - last loaded 22570273592
com.symantec.kext.SymEvent2 10.1.0
org.openafs.filesystems.afs 1.3.82
com.apple.driver.InternalModemSupport 2.4.0
com.apple.iokit.IOBluetoothSerialManager 2.1.8f2
com.apple.filesystems.autofs 2.0.2
com.apple.driver.AppleHDAPlatformDriver 1.7.1a2
com.apple.driver.AppleHWSensor 1.9d0
com.apple.driver.AppleHDAHardwareConfigDriver 1.7.1a2
com.apple.driver.AppleHDA 1.7.1a2
com.apple.driver.AppleUpstreamUserClient 2.7.5
com.apple.kext.ATY_Wormy 5.4.8
com.apple.Dont_Steal_Mac_OS_X 6.0.3
com.apple.ATIRadeonX1000 5.4.8
com.apple.driver.AppleGraphicsControl 2.8.15
com.apple.driver.AppleACPILPC 1.0.8
com.apple.driver.AppleHDAController 1.7.1a2
com.apple.driver.AudioIPCDriver 1.0.6
com.apple.driver.AppleIRController 113
com.apple.driver.ACPI_SMC_PlatformPlugin 3.4.0a17
com.apple.driver.AppleLPC 1.3.1
com.apple.driver.AppleBacklight 1.6.0
com.apple.driver.AppleTyMCEDriver 1.0.0d28
com.apple.iokit.IOFireWireIP 1.7.7
com.apple.driver.CSRUSBBluetoothHCIController 2.1.8f2
com.apple.driver.AppleUSBMergeNub 3.4.6
com.apple.driver.CSRHIDTransitionDriver 2.1.8f2
com.apple.driver.AppleUSBHIDMouse 1.2.4b3
com.apple.driver.USBCameraFirmwareLoader 1.0.9
com.apple.iokit.IOSCSIMultimediaCommandsDevice 2.1.1
com.apple.iokit.SCSITaskUserClient 2.1.1
com.apple.iokit.IOATAPIProtocolTransport 1.5.3
com.apple.driver.XsanFilter 2.7.91
com.apple.iokit.IOAHCIBlockStorage 1.2.2
com.apple.iokit.AppleYukon2 3.1.13b2
com.apple.driver.AppleFWOHCI 3.9.7
com.apple.driver.AirPortBrcm43xx 366.91.21
com.apple.driver.AppleFileSystemDriver 1.1.0
com.apple.driver.AppleUSBHub 3.4.9
com.apple.iokit.IOUSBUserClient 3.4.9
com.apple.driver.AppleAHCIPort 1.7.0
com.apple.driver.AppleIntelPIIXATA 2.0.1
com.apple.driver.AppleEFINVRAM 1.2.0
com.apple.driver.AppleUSBEHCI 3.4.6
com.apple.driver.AppleUSBUHCI 3.3.5
com.apple.driver.AppleACPIPCI 1.2.5
com.apple.driver.AppleRTC 1.2.3
com.apple.driver.AppleHPET 1.4
com.apple.driver.ApplePCIConfigurator 1.0.4
com.apple.driver.AppleACPIButtons 1.2.5
com.apple.driver.AppleSMBIOS 1.4
com.apple.driver.AppleACPIEC 1.2.5
com.apple.driver.AppleAPIC 1.4
com.apple.security.seatbelt 107.12
com.apple.nke.applicationfirewall 1.6.77
com.apple.security.TMSafetyNet 3
com.apple.driver.AppleIntelCPUPowerManagement 76.2.0
com.apple.driver.DiskImages 199
com.apple.BootCache 30.4
com.apple.iokit.IOSerialFamily 9.4
com.apple.driver.DspFuncLib 1.7.1a2
com.apple.iokit.IOHDAFamily 1.7.1a2
com.apple.iokit.IOAudioFamily 1.6.9fc5
com.apple.kext.OSvKernDSPLib 1.1
com.apple.driver.IOPlatformPluginFamily 3.4.0a17
com.apple.driver.AppleSMC 2.3.1d1
com.apple.iokit.IONDRVSupport 1.7.3
com.apple.iokit.IOGraphicsFamily 1.7.3
com.apple.driver.AppleUSBBluetoothHCIController 2.1.8f2
com.apple.iokit.IOBluetoothFamily 2.1.8f2
com.apple.iokit.IOUSBHIDDriver 3.4.6
com.apple.driver.AppleHIDMouse 1.2.4b3
com.apple.driver.AppleUSBComposite 3.2.0
com.apple.iokit.IOSCSIBlockCommandsDevice 2.1.1
com.apple.iokit.IOBDStorageFamily 1.5
com.apple.iokit.IODVDStorageFamily 1.5
com.apple.iokit.IOCDStorageFamily 1.5
com.apple.iokit.IOSCSIArchitectureModelFamily 2.1.1
com.apple.iokit.IOFireWireFamily 3.4.9
com.apple.iokit.IO80211Family 216.1
com.apple.iokit.IONetworkingFamily 1.6.1
com.apple.iokit.IOAHCIFamily 1.5.0
com.apple.iokit.IOATAFamily 2.0.1
com.apple.iokit.IOUSBFamily 3.4.9
com.apple.driver.AppleEFIRuntime 1.2.0
com.apple.iokit.IOSMBusFamily 1.1
com.apple.iokit.IOStorageFamily 1.5.6
com.apple.iokit.IOHIDFamily 1.5.5
com.apple.driver.AppleACPIPlatform 1.2.5
com.apple.iokit.IOACPIFamily 1.2.0
com.apple.iokit.IOPCIFamily 2.6

Any help? This problem happens without fail after about an hour or so of use, regardless of what programs are being used. I've updated OS X fully, repaired Disk Permission, verified Disk and Disk Permission. Any other possibilities?