I'm restarting this thread with updated info, as this problem hasn't been solved with 10.5.2. Below I mention Acomdata drives, but this problem also seems to affect iomega drives, can someone please give me the exact model number if possible and or a picture of the affected drive, as I'm trying to gather as much info as possible about this problem. Thanks... The Problem: Computer is up and running with usb drive(s) mounted and working fine. After restart or sleep, CERTAIN drives aren't visible - they don't show up on desktop, in disk utility, in system profiler, or in disk utility started from os x install disk. in 10.5: both sleep & restart cause problem to occur in 10.4: sleep causes problem to occur, but restart doesn't cause any problem. when using a drive that exhibited the "problem" in 10.5; putting computer to sleep and waking on 10.4 causes drive to improperly eject, prompting "device removal" screen upon wake; drive disappears and can't re-mount until power toggled. The Quick Fix: Toggle hard drive power (turn hard drive off and on) Problem is affect by (at least): enclosure manufacturer/model (in my household, the only 2 drives exhibiting this problem are acomdata usb enclosures with logic board: b112 rev 1.7 & b112 rev 1.5) *my maxtor, storecase, and other acomdata drives/enclosures don't exhibit this problem* i believe some iomega drives have this problem too, can someone please give me the model # of their drive if they are having this problem? Problem is not affected by: partition map scheme volume format physical usb port (on mac) particular computer (happens on both leopard machines - mini & powerbook, and one tiger machine - g5 dual 2.0) hard drive manufacturer Things that don't fix it: SMC reset PRAM reset (option+apple+p+r at startup) PMU reset (which also resets pram & nvram) 10.5.2 / 10.4.11 Combo Updater manually installed Console Messages (messages appearing after restart has occurred and drive hasn't shown up as expected): *Leopard* 2/21/08 3:17:21 PM kernel USBF: 0.842 [0x2aa7d00] The IOUSBFamily is having trouble enumerating a USB device that has been plugged in. It will keep retrying. (Port 1 of hub @ location: 0x3d000000) 2/21/08 3:17:21 PM kernel USBF: 2.163 CSRHIDTransitionDriver[0x2ae5980](IOUSBCompositeDevice) GetFullConfigDescriptor(0) returned NULL 2/21/08 3:17:21 PM kernel USBF: 4.682 [0x2aa7d00] The IOUSBFamily was not able to enumerate a device. *Tiger* Feb 21 14:53:21 migG5 kernel: USBF: 2335.189 [0x42aa000] The IOUSBFamily is having trouble enumerating a USB device that has been plugged in. It will keep retrying. (Port 2 of hub @ location: 0xb000000) Feb 21 14:53:25 migG5 kernel: USBF: 2338. 13 OHCI driver: OHCIRootHubPortPower bit not sticking (0). Retrying. (this goes several times) Feb 21 14:53:25 migG5 kernel: USBF: 2338.813 [0x42aa000] The IOUSBFamily was not able to enumerate a device. In Conclusion: I'm interested if anyone else can duplicate this same problem or something similar with any other drives/enclosures (other then the 2 acomdata enclosures I have). Then we can look at the similarities and hopefully find out and fix the problem. If no one else has this exact problem, perhaps it really is just an acomdata thing (as applecare suggested today on the phone). Perhaps it's a chipset issue? Any insight appreciated! -Brian P.S. I've posted this in a few forums and if you're interested in reading more about this problem, I'll be keeping any relevant info/updates I find on my blog (Corewerkz).