I doubt that the ground has anything to do with it!
Thanks a lot for your answer.
So you do not belive the non ground could cause this kind of instability? A friend claimed he could feel some low tickling creeping current on the computer case, however I can not, but I am sure he is right. This can not "build up" something that leads to a instant reset much later?
Most likely internal protection in the PSU to sensitive.
What does that mean? That there is something fault with the PSU or that is sensitive to some other condition?
The PSU is a "COOLER MASTER SILENT PRO ATX12V 2.3 600W".
Then again you could leave the computer in the kitchen for a week.
The only "problem" is that it would not be appreciated by my wife.
It is not even sure it would reset in a week, it has happened perhaps four times and very unregular.