Hi, I have a core duo iMac that has been working fine. The other day I did a wipe so I could sell it, and during the reinstall it ejected the second disc because it was dirty. I cleaned it, and all seemed good when I put it back in. Now, the computer works but sometimes gets a gray screen that says something like "There has been an error and you need to restart your computer." I wanted to reinstall again, but now it gives me that screen anytime i try to boot from the cd. Help?