I don't believe it's a temperature issue, and definately not a dust issue. When I installed my new power supply I did a pretty thorough cleaning of dust.
As far as temperatures go nothing is really all that hot.
Vid card: 58C
CPU: 42C (at 100% load due to BOINC)
HD: 38C-42C (depends on how close they are to the intake fans)
Is it possible that this is a software related issue?