but how can that afect my PC? Offline is OK, it should crash then also...
Sorry, I did not develop my argument clearly. Sure the power saving etc. works when the device is not connected to the internet, but they are background processes, that may be conflicting with something that starts when you make an online connection? It was really an extension of my "deadly embrace" theory.

My usual style of troubleshooting is to turn all this off until I get a stable system, then gradually restart them until I find the culprits. It is really just an elimination process

I am not too sold on DDos/DoS at the moment. The people who do that sort of thing would want you to know that it was them or at least that it was a deliberate attack? That seems to be the way their egos work, unless you are some major corporate entity? For example, can you think of anyone who would want to do this to you?

Well my idle temps are around 23C and go up to about 35/38 on full load with a room temperature of about 21C (it does not get very hot here). That is why I would suggest 15-20 above room temperature. Although your processor is probably safe at 85C, that does not mean that your system will work properly. Instability with Athlons seems to creep in around 60C in my experience.

Please check your BIOS and make sure that you are not overclocking anything...........video card is a favourite for producing the symptoms you describe

Cheers