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.