Thought I'd join the club here. I'm running Windows Vista x64 RC1, build 5600. Everything ran smoothly since I installed it shortly after its release, but about two weeks ago any USB storage device would fail - "USB Device Not Recognized". I have a printer and a wireless keyboard/mouse connected via USB, and I've also used a gamepad without problems. But neither external harddrive, memory card reader nor Canon camera works.
However, when starting Windows XP 32-bit (I have dual boot) it all works fine. I even got it working on Mac OS X Tiger!
So I formatted, sure it would solve the issue - yet it didn't. Still works in XP and OS X, though.
Further machine specs: Custom built AMD Athlon 64 X2 4600+, 3 GB TwinMOS PC-3200, 2 x WD 200 GB S-ATA harddrives, GeForce 7900GT. Running freshly installed Windows Vista x64 5600, only newest ForceWare installed.