Buffer I/O error on device sr1

I'm running Intel Core 2 Quad 2,4Ghz processor.
Asus p5k-e WiFi ap motherboard. 4 gig ram and a SATA disk.

When I'm starting the Ubuntu Live CD, all is good. I can choose between the menus. So choose normal startup, and Ubuntu loads the loading bar, then I get an error saying "Buffer I/O error on device sr1. Logical block [a number that increases each time i get the message]". There is also a "squasfhs" error message of some kind, but it goes to fast for me to write down.