As far as I can see, gcj suffers a bus error trying to compile even the trivial "Hello World" program (see #594830) since last summer. This problem is exhibited in GCC 4.4 and GCC 4.6 releases.
Only on kfreebsd-amd64 and only on some machines. gcj fails under fash.d.o, but not fano.d.o, it works under my real machine, fails under "qemu", but works with "qemu -enable-kvm". I have no idea what is going wrong. Petr