My computer problem is solved: technician said it was due to lot of dust between air_cooler and processor. He has cleaned between both pieces, removing all the dust. Now all seems to work, I rendered a picture 2h50' long without freezing. Will post here tomorrow the pic which is a (classical) test between ultra mode (800x600) and final mode (say 3200x2400 then reduced to 800x600) to see the difference. Nice to be completely here, and strange thing, Guitta, it was the same problem you had (A chance for me since two weeks ago I already changed motherboard and processor of my other computer, after a manipulating error from my part). Yves