Temporary bug in thrax-1.2.2 where AssertNull and AssertEmpty are not being properly registered. This will get fixed soon, but in the meantime as a temporary fix please replace src/lib/walker/loader.cc with the version of loader.cc at http://openfst.cs.nyu.edu/twiki/pub/Forum/GrmThraxForum/loader.cc, and reinstall. [As of thrax-1.2.3 this is fixed.]
In thrax-1.0.2 there is a problem linking the binaries in src/bin on 64-bit linux. If you encounter this, please do the following:
Replace thrax-1.0.2/src/bin/Makefile.in with the version here.
Rerun configure in the top level Thrax directory
Rerun make
The final statement in an input grammar file needs to be syntax-error free. The parser dies mysteriously with no helpful debugging output if the last statement is poorly formed.