definite weirdness.

what do you mean by "longer gaming session"? i've been in for 6+ hours without any issues (using xp and vista). are you talking all day? (not that it should make a difference, just trying to understand)

how much memory do you have on the affected machine? how many wows are you normally running on it at the time? (machine specs please)

are you running the latest? v1.7r?