"Hi, I just spend a few hours compiling qt. But without mt support. I don't even know what that is, actually. But is that a big deal? Should I recompile?"
mt means multithread support. Most Qt based applications do not need mt. A few, like kbear, need multithread support and will not work without it.
Personally, since I first tried to install kbear I have always included mt. I think that it should be the default in Qt.
Be prepared. Create a LifeBoat CD.