This thread sure does sound suspect. The KDE version boots fine, the old Mint version boots fine, but the new Mint 4 main doesn't boot?
Are you absolutely sure your problems weren't related to a bad cd? Did you burn it at 4X speed in a RAW mode and then check the md5 sum with the one posted on the download site?
A bad download, or bad cd, or bad burn can really cause some confusing problems.
Just a couple random thoughts.