Polar,
A couple questions if the answer is yes to each one, go to the next. If no, then heck if I know
1. Is the USB port built in to the motherboard?
2. Does the board have a Via chipset in it?
3. Was it built sometime in 2001 (approximately)?
The basic problem is that circa 2001 via chipsets and onboard ports on MBs don't play too nicely together either at all, or as in your case, in some applications. The only reliable solution that I've found after a lot of searching through troubleshooting and tech support is a USB to something else adapter (in my case USB to mouse port).