I've gone inside the tower, vacuumed wherever I could reach and used compressed air blasts also. Relatively little dust. No cooling liquid leaks. I've crossed my fingers.
Well, today I was importing images, and when rendering about 50 of them, it started going to sleep again as temps got up to 160 or so on CPU A and 190 on CPU B. CPU fan speeds ranged from 1200 to 3000 rpm. UGH. Seems like no one else is having this problem. Looks like I may need to take this critter in for a full physical.
At home, I only have an old 2x2GHz G5 but I tried to export 50 photos (1Ds3 raw files. Both slideshow and web export). After 20 minutes, temperature were around 160F for both CPU. CPU usage was almost always around 95-100%. Fans were in the 300-550 rpm range with an occasional peak to 750 rpm. I used iStat Pro for these readings.
You 2x2.5GHz might run hotter than my old Mac.
See the screenshot below.