this is a known problem not normally crashing a pc though. I have a pc that will not start if any usb devices are plugged in at boot. This problem is solved in my case by the fitting and correct setup of a pci usb2 card. Are you sure you have it correctly set up? If you have a usb2 device plug it into your pci card and see if you get the message this device could work faster in a usb2 port. If so the system has not been correctly set for the card.