ooo signal 11!
Fun stuff 
segfaults are always fun.
ok now more info:
- what client are you using( i don't know what ubuntu repository has)
- have you tried a "newer" client
- what qvm are you trying to run/ is it the one included with the repo if so what ones in there.
id prob recommend trying a new client maybe the issue is fixed its the easiest option.
any other advice i would need more info. i am great at causing segfaults not so much fixing em

EDIT: it wouldn't take much but it would be possible to make tremulous do a BT when it receives a signal i don't know if its available on windows but ive played around with execinfo.h with a few of my personal coding projects to give me a BT without bothering with gdb.