I'll Go with what the others suggested. Namely
USB Cable - Try another Usb Cable. Somtimes USB cables cac act in unpredictable ways, and I've usually found that trying a couple of alternative ones solves the problem. You probably have a compaitable one lying around as Mini USB is pretty common, especially for cameras and portable HD's.
USB Port - try using some of the other usb ports. Often, Some of they may not have enough power, and may end up causing problems. On a Desktop it might be worth trying one of the ports on the back, as that might work.
Reset - Try resetting the device before trying to connect. It has often stopped funny behaviour for me.
Safe Mode - Try booting into safe mode (usually by pressing F8 when the machine is starting up) and try connecting the Gen3. I've often had issues in vista when connecting USB drives, HD's etc, but they usually work fine in Safe mode. THis will at least allow you to narrow down the proble, i.e. is it a device issue or a vista issue
.
Another computer - As Mentioned earlier, if you can beg, borrow or steal access to another computer, preferable one running XP, you might be able to narrow down if the fault is with the Device or the Computer.
Hope one of these suggestions help