TMbuilder works fine on my computer (Win7 64-bit), but it sometimes introduces stuff like "'" instead of apostrophes. It also spits out UTF-16, which I don't like. TM Maker in the LF Aligner "Grab Bag" also adds these HTML characters.
The best free TMX creator I have found is actually inside the now free Heartsome TMX Editor:
Tools > Convert to TMX … produces perfect TMXs every time!