I tried burning the Sabayon 3.0 RC1 DVD with Nero Express 6.0 on Windows. The program said the burn was successful. When I checked the disc using the shareware CDCheck, it said that the compressed image file is corrupt. I'm using HP DVD-R media on a TSSTcorp CD/DVDW TS-L532A laptop burner.
Did you download the ISO with bittorrent or directly from the mirror? Bittorrent is the safer way to go because it keeps the hash and md5sum all in order for a good burn nearly every time.
How fast did you set the burner to burn? Sometimes you will get a bad burn if you spin that disc to fast. I suggest retrying the burn, if you still have problems. redownload the ISO. Or wait till the 13th for the new version! =]
My solution was to use a different burning program. At first, I had problems burning the disc in Kubuntu using K3b. That is due to a bug in the version of growisofs included in the distro. Upgrading growisofs did nothing. So I decided to boot into Windows. Burning in Nero Express 6 resulted in a corrupt DVD. Finally, I burned the DVD in CDBurnerXP Pro 3 and got a good disc.