Currently Being ModeratedJul 1, 2013 9:30 AM (in response to papaloco)
Certainly sounds like an overheating issue. What are the ambient temps in your house or workplace? Lots of palces in the Western US are experiencing record high temperatures.
You can check to see if you have a runaway background process that is runing up the temps. Use the instructions in this Apple article:
Currently Being ModeratedJul 1, 2013 11:12 AM (in response to papaloco)
This condition (called thermal runaway) was common back in the early days of the PowerMac G5s. Search the G5 archives using "thermal runaway."