I just compiled Vala 0.5.5, and used it to build the revision 2259 of global menu. The build went well, and I can add the applet to my panel.
The problem is that the preferences menu is blank (just a blank maybe 40x40 pixel window) with nothing in it (I resized it to check). Of course, the global menu functionality is not there at all as I can't see it on the panel.
The only reason I built it all from source is that I had the EXACT same problem with the stable build in the PPA.
I will file a bug report if there isn't an immediate solution to the issue. I've already posted on their wiki.