That is a typical problem cause by one of three different items.
1st. CPU overclocked to high.
2nd. RAM is second likely canidate. Damaged or mis-seated.
3rd. Cards mis-seated.
Have you moved the computer lately?
How much dust is inside the case?
Do you smoke in the same room as the computer?
Dust and smoking cuase overheating and since you have a AMD chip (which is hot to begin with) adding dust or smoke is a no-no.
Clean you motherboard, reseat you cards and RAM, and
make sure your CPU fans still operate.
Let us know if any of this helps.
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