Pidgin crashes during sipe login if LANG env. variable is tr_TR. If you set LANG=C there is no problem. I have tried it on 0.8(lucid), 0.9(natty) and 1.11(oneiric) pidgin-sipe ubuntu packages.
I tried to reproduce the crash on Ubuntu Lucid but my Pidgin runs in Turkish without problem. SIPE does not have tr_TR translation at all, so the bug is maybe in Pidgin or somewhere else outside the plugin. Please attach here a backtrace after your crash occurs, see [url=http://developer.pidgin.im/wiki/GetABacktrace]this instructions[/url] how to do it.
What is the content of your /var/lib/locales/supported.d/local file?
Can't reproduce with "LANG=tr_TR /usr/bin/pidgin --debug" on Fedora 15.
Closing as INVALID for now, but keeping comment posting open. FYI: once you attach the requested Pidgin debug log and the GDB backtrace (that shows that the crash is caused by libsipe.so) to this bug report, it will be automatically opened again.