You might check to make sure the necessary files are on the Repair CD.
How are you selecting the DVD as a Boot Device, in the bios? If so, are you saving the option before exiting?
Can you use a boot device menu to select the CD?
If none of this works, you might explain how your system is burning the CD and what type of CDs you are using. I don't remember if there are options when it burns, but if there are, you might try slowing it down.