Does the keyboard connect using usb (square connector) or PS/2 (round connector)?
Some computer BIOS's can get a little "funny" with USB keyboards.
EDIT: Just read through again, saw "Swapped USB ports".
In that case, does the PC have a PS/2 port, and do you have a keyboard to try it out with?
Disconnect all other devices other than the keyboard and screen. If another device is maulfunctioning it could be interfering with the boot process.
message edited by thomasad