Originally Posted by saturnotaku
Bolded parts are likely your problem. You have an off-brand power supply whose total wattage is less than what NVIDIA recommends (575W minimum for a GTX 280). Upgrade your power supply to at least 600W and choose from any number of name-brand units (Corsair, OCZ, etc). If you also had a similar problem with another type of system, you may also have some issues with the power running to your house. In that case, you should also invest in some kind of surge protector/battery backup.
Thank you for the answer, I will check the power running to my house, and replace my power supply (The reason, why I was still using my 600 W power supply is that my 1000 W be quiet power supply isn't quiet at all
, but now I will give it a try ). What I have to mention: I had no serious problems with my geforce gtx 280 for the first 2 month; errors, random pixels have appeared on the desktop since I came home from my holiday (during my holiday, nobody used my pc).