i agree with disophis, it does sound very much like the ram, or be it the ram slot, i cant help but think of the cpu aswell, but if it was the cpu overheating in someway it would simply restart or...

wow dlh, got it in one there, lol im curous though, what did u try when attempting to go in to safe mode ingetborg? and if it wasnt working with F8 then dlh, what could b the cause 4 tht?
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im with caperjack, sumhow i dnt think its faulty ram, it sounds to me like ur ram is possibly gettin hot or its heat in some way that is causing it, another thing tht u could try (just to add sumthin...

need more details than that, we will work out were the spaces are meant to be, lol, for now use the xp on screen keyboard in accesories :P