Mouse and keyboard wouldn't respond

[Jynweythek]

I have this strange problem. Every once in a while my keyboard and mouse (both ps/2) stop responding all of the sudden. And it can happen whether few minutes after I just turned the computer on or few hours later. And it's not like computer locks up, I can be playing a game or listening to music, all the programs keep running fine, it's just the mouse and keyboard stop working. Any ideas what could it be?