sorry for the late reply; your mail looked like spam (subject: "my message") so i didnt look at it yet.
do you have a link to that launchpad build? i'm curious.
as for your problem: i dont know how jabber does his dns, maybe it does it on some own dns server in its own network ? in that case of course resolving .onion wouldn't work.
if they use libc functionality, they may use a function that's not hooked (by mistake), or it is possible that they do the dns lookup directly or via some library like firedns which completely sidesteps the libc hooks and does the socket i/o on a low level.
you could ask some of the jabber developers about this or look at the source code, or try to run it under strace myprog 2>&1 | grep -C 10 ".onion"
, which could give some clues about what's happening.