Sounds like a faulty card or somekind of conflict with XP. Maybe try the card in another machine and see what happens.
Z
I just bought a usb 2.0 pci host card to upgrade from 1.1. When i booted up after I plugged it in, my computer locked-up after about 20-30 seconds. It seems to be at the very end of the boot-up, right after I get the "new hardware found" message. The card is generic (I think), with an NEC chip. I have Windows XP Home, which I updated fully through MS website, but problem occurs the same. Problem goes away, with no side effects, when card is removed and re-booted. I have a P4 2.2 with 512M ram. Lock-up occurs with card plugged in each of my open slots (to cover my bases). Any ideas/suggestions would be much appreciated. Thanks.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic