A few months ago I asked Christian Marillat, who maintains and does all the packaging for the debian-multimedia repository, to take a look at mplayer-mt. He has kindly added the package to the testing and unstable sections and updates them regularly. I just rebuilt his latest for Mepis 8.5 (OK, that was my main motivation, he's a lot better packager than me, I need to leech off his expertise), and he has managed to fix the "unknown version" bug that frontends such as SMPlayer throw up.
Anyway, I don't know if his debs are Ubuntu compatible, but it should be simple to rebuild them if not