Mythbuntu is installed from an ISO file that is al little larger than can be burned to a CD ROM. While every computer for the past decade was bult to use CD ROMS, not every server was built with a DVD player or to boot from a flash drive.
The fix for the oversized ISO is to written to burn to a DVD or flash drive.
Please let me know what files on the MythBuntu 12.04 ISO contain software downloadable later so can be easily removed in order to get the size do to one that can be written to a CD. Thanks