Should there be two things using the same IRQ?

I have NEC PCI to USB Open Host Controller and Radeon 9700 Pro both on
(PCI)19.

I also have NVIDIA(R) nForce(TM) Audio Codec Interface and Standard OpenHCD
USB Host Controller both on (PCI)21. Will this cause problems?

The reason i ask is this.. I had a razer diamondback mouse that would
disconnect from usb, and connect again by itself, constantly. so, i'd be
playing a game, and my mouse all the sudden dies completely, for a few
seconds until it connects itself again. it only seems to happen when i'm
playing games so far. i thought it was the hardware(razer mouse), but now i
have an old logitech usb mouse hooked up and it's doing it too. I have
reformatted and reinstalled windows fresh. It didn't fix the problem. Could
the IRQ thing be the problem? Or, is my USB hardware failing on me? I
haven't had problems with any other USB item other than my mouse. the damn
mouse... it's crippling as far as playing games.