I had a similar issue recently with 2 different machines - random freezes, except sometimes the mouse would still work. Would happen under load & whilst idle. In the end, I reformatted one of the machines (2990wx) and slowly added my software back on 1 at a time and (so far) all seems fine. The other machine I simply did a Windows update - I think that's probably what caused both the problems. So in other words, if that sounds like the problem your facing, check you're on the latest Windows version. Good luck!