This is the wrong place to ask for QMC2 support, but regarding your specific issue, see here:
http://sourceforge.net/forum/forum.php?thread_id=2179311&forum_id=658600Without proper support for libphonon, you won't get 0.2.b5 (SVN) working! It has the Phonon parts of the code enabled (but nothing real new yet). Use the latest release please (0.2.b4) or a Phonon enabled Qt 4.4 build on Ubuntu.
When using Qt 4.3, the libary dependency will be automatically removed, BTW. Qt 4.3 doesn't support Phonon at all.