I am running Vista 64 bit, with 6 gb memory and a core-2 Quad processor. I've had an external USB hard drive running fine for many months. Recently I bought a scanner and a thumb drive and both of these run fine as long as I don't hook up the hard drive. When I add the hard drive, Vista can no longe "communicate" with the other devices. In order to use the scanner I have to unplug the hard drive and plug in the scanner. I have a ticket open with Microsoft now for several weeks with no useful information provided so far.

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.