Garp! Do you really render any mode in two pass?
I have add kdenlive-svn repo and update and upgrade system. It reinstall current kernel (???), delete python-mlt and change mlt4 to mlt5.
MPEG2 2 pass work, xvid4 1 pass work, but xvid4 two pass render don't work!!!
But I don't purge anything just upgrade the system!
I'm running Ubuntu 12.04 x64