I'll post this in here too, because it's mostly Xee-related anyway:

http://wakaba.c3.cx/releases/mac/TheUnarchiver1.5.zip

This version should hopefully fix the problems with loading archives! Anybody who had the problems, if you want to confirm that it has been fixed, install this and re-install Xee (or just delete the Frameworks folder from it if you copied it oveer)!