Therion fails to compile with GCC 4.1 due to a couple of problems.
There's a patch in this bug report:
http://bugs.debian.org/356875
Direct link to the patch:
http://bugs.debian.org/cgi-bin/bugreport.cgi/therion-0.3.9-ftbfs-with-gcc-4.1.patch?bug=356875;msg=14;att=1
Cheers,
Olly