According to most search results on that error, it is either a bad DVD drive or a bad burn of the ISO image to the DVD. If you know your DVD drive works fine (have recently used it in Windows, for example), then you likely have a disk that wasn't burned right.
If you can, download the ISO file directly yourself here: http://www.linuxmint.com/download.php
. Check the md5sum of your downloaded ISO to make sure it matches the value shown at the top of the version page that you downloaded. Burn the ISO image to a DVD, or use a program like UNetbootin to make a live USB instead.