WHAT i would do in this case will start the MAC using the CD drive, with the MAC OS X reinstal software, go to disk utility and repair the hard drive. this will not delete your files, and as far as a know this migth be a hard drive issue. try that, and i really dont think it that there is an issue with the graphics card,.... do im wrong??? any wise person that can tell me that im wrong?? Mr. Rich.d Mayer.