|In some older models and maybe some new ones there is a fuse (might be labeled R or H or F or even C) that can blow if you plug and unplug the ps/2 type keyboard in while power is on.|
Usb keyboards are a bit different. They may need a bios setting but it can only be done from a ps/2 keyboard plugged in.
Can't you borrow one to test?
Why did it take me over a year to phone in a problem to ATT?