USB I/O problems?

Well I have (in my unqualified opinion) a very strange problem... I think I have it rather narrowed down though.

Normally, almost every single usb device on my computer does not work at all. When I attach USB drives (or other mass storage devices), and try to open them in explorer it informs me that "J:\ is not accessible. The request could not be performed because of an I/O device error." When I plug in my ipod and open itunes, it hangs until I remove my ipod (that is, its open in the task manager, but it dosen't have a window). Etc. etc. TV tuner, webcam, everything acts the same way. The only exceptions are my wireless mouse, which is hooked up through usb (and NOT a PS/2 to usb connecter, for what it's worth) and my midi keyboard (a yamaha DGX-220), which I have only tested receiving midi data from my keyboard, not send to it.

Everything works just great as soon as I go into my bios and disable the "USB 2.0 controller" setting, which, of course, forces me into USB 1.1 for everything.

I run a dual boot on XP SP2 and a fully updated Vista Business. The problem's the same for both (although I had it while I was in XP single-boot and vista single boot. so dual boot cant be the culprit, though I doubt it could have been in the first place)
All six or eight USB ports on my computer have this problem, and they have been thoroughly tested.

Anyone seen this before? any ideas on how to solve it?

My specs are:
ASUS A8N SLI Deluxe
Athalon 64bit 3500+
GeForce 7600GS x2 (sli mode)
2GB ram
Windows XP SP 2 (32 bit)
Windows Vista (32 bit)