I am also facing the problem with showing the account numbers instead of the name.
The odd thing for me seems to be, that it shows the numbers only for the online contacts.
The offline contacts are shown with their names, or alteast it takes longer for them to show
them as numbers. But I just tested qip 2012 v4.0 build 9320 (latest build) and it has shown
the names. I installed it yesterday and everything was fine. Today it autostarted and ran about 5 to 6 hours (came home at 17:45 and started it at about 18:00 and just closed it at 23:25 o'clock). These 5 hours it has always shown the names, not the account numbers. So I assume
that jitsi has some kind of bug (and maybe other messengers aswell) or that qip got a workaround.
And a feature request for the devs => please ditch java and make the app start faster on old computers like my P4. QIP only needs some Seconds to fully start here, while jitsi takes about a Minute or so (not tested with a stop watch, but the First impression was, that my computer boots
faster with qip than with jitsi and that it is more responsive and usable earlier).