Hi guys. I have problem with iMac g5 1.8 5200nvidia 17 inch. It has artifacts but i explain when it happens. When i turn on computer and system is loaded artifacts starts showing. Then mouse didnt work great and i have to turn off with power button. Nextly i Turn on machine (second boot) and it looks the same. The third boot is always succesfull and there arent any artifacts. To sum up on third boot i can normally work on computer and these 3 steps are always the same and happen in this order. I would be glad if somebody would help me.