Comment 6 for bug 421208

This problem has been fixed upstream, see http://filezilla.svn.sourceforge.net/viewvc/filezilla?view=rev&revision=3445

The root cause was that threading wasn't initialized in libdbus, leading to plenty of race condition causing the observed crash.

Two possible workarounds for this issue until the FileZilla package in Ubuntu gets updated:
a) Disable the "Prevent system from entering idle sleep during transfers and other operations" option in the settings dialog of FileZIlla
b) alternatively install the ibus-gtk package, if it gets loaded during startup of FileZilla it initializes threading in libdbus before FileZilla calls any function from libdbus.