The question has been closed for the following reason "Duplicate Question and the question is answered, right answer was accepted" by Mattophobia Mar 20 '11 at 19:54
Try booting into the install disc see if it is the os installed or hardware problem, if that works then if you have no important info on the computer I would restore it. Also you could boot it into target disc mode if you have another Mac around to transfer files off. Also I know there is an option to where your "old mac" files are saved so you could do that as well. A friend of mine had this problem but with kernal panicks. The restore or hard drive imaging fixed it so I would think it would fix this.
answered Feb 13 '11 at 20:18