I've finally gotten Mono working on my system.
I have tried compiling it in the past, but never actually made it perform well. I have used built-in GC (Garbage Collector), but it made it crash on my pretty ancient system (GCC 2.95.3, GNU libc 2.2.3). If I don't use GC at all (--with-gc=none), it borks with mysterious error message of "NullReference where Object as expected" (or something like that) for a bit more complicated code (like 20+ lines of C#, meaning, I'm not even able to recompile Mono from CVS after that, because it requires a working Mono installation; bah, bootstrapping sucks). Since newer GCC's seem not to show up this (nobody else complained), it's most likely a GCC bug.
Luckily, there's an option for another GC, one of Hans Boehm, and that's what made it work, provided I compile it with "--enable-threads=pthreads". For the record, I've used gc 6.3alpha4 version from January 1st, 2004 — I don't mind occasional bugs, as long as it doesn't bork it completely.
So, if you Mono segfaults in "GC_mark_show", that may be the culprit.
Mono from CVS is now being compiled, which leaves me with some time to actually update database for "common Serbian computer dictionary". Hope to put it online tonight, and redirect all requests from prevod.org/recnik to new dictionary.