The BIOS has been updated
The chipset has been updated
Tried different USB ports
All hardware drivers are up to date
All Microsoft updates installed
I have done a software update from the original Vista CD
There are no relevant error messages in the event viewer and no relevant error messages in the problem history.
I am also experiencing the well documented (on this site) Vista hangs, unpredictable and random. Hangs for a minute or two and then catches up. Again no relevant error messages in either event viewer or problem history. Everything stops but the mouse works (not USB), and I can close open folders but can't open anything. I doubt this is related to the USB issue but I'd believe anything at this point.