Install disk ejects during restart

Yesterday, I ran Onyx on my macbook and it said I needed to repair my disk by running the repair from disk utility after the macbook restarts with the install menu. Worked great, runs much better now. Thought to do the same with my mini.

Problem is when I restart (holding C while it does), the disk always ejects. This did not happen with my macbook. I don't see anything visibly wrong with the CD itself. Maybe a problem with the keyboard? I'm using a wireless Logitech keyboard.

My mac mini is running OS 10.6.7, 1.83 GHz Intel 1 GB 667 MHz DDR2 SDRAM

Thanks for any input!

Which disk are you using to boot the Mac Mini? Install disks are specific to the hardware. You can not use your MacBook install disk to boot the Mini as it will eject or refuse to start.

If you are using the correct disk on the Mini, it may be a dirty lens in the optical drive. Buy a can of compressed air and blow a few short blasts in the drive slot to see if that cures it.