User fthieme recently reported, that version 1.8.4.0b1 is not buildable in his system. (Arch Linux, Qt 4.5.2)
We found a solution, svn trunk is fixed now.
If you can't build 1.8.4.0b1 - try to use svn trunk version.
Here is instructions: http://monkeystudio.org/wiki/Svn