Remove the PCI card and see if the system runs as you expected it to. If it does return to normal return the USB controller and get a different brand. I use Adaptec's with no problems. Make sure you delete it from the device manager and remove the software.
Not sure, but if the PCI card is faulty it might play havoc with the BUS. Let us know.
and life goes on...
have just bought a belkin usb 2.0 3port pci card as 3 of my other usb ports wont work. installed driver from cd turned off pc fitted the card turned pc back on found new hardware wizard comes up tryed to install automaticly it searches for usb controller but it cant find it then ask if i want to search the web tryed a web search doesnt come back with anything tryed to install straight from the cd doesnt find it went to belkins site found the latest drivers and installed them still no joy found some probs with my programs when the card is in my pc windows media player will not work and sends some other programs all crazy anybody got any ideas this is doing my head in with only one usb port working
windows xp pro sp2 (5.1.2600)
packard bell imedia
2 20gig harddrives
gigabyte i810 motherboard
intel coppermine-128 celeron II 903mhz
american megatrends bios 3.0w