I'm using sunabs svn PPA on Natty 64bit & I can't get x264 encoding, there's a big red cross against them in the render options. :-)
I have libx264-106 & 115, x264 Ubuntu package 2:0.106.1741-3, libmp3lame0 3.98.4.0ubuntu1 installed.
I have ffmpeg 4:0.6.2-1ubuntu1, libavcodec-extra-52 and lib avformat-extra-52 installed.
Using sunabs 32bit svn build on my laptop does give the x264 render options, so I guess I have some kind of mixed up dependancies on the 64bit machine.
I also have ffmpeg from git compiled from source with x264 support at /usr/local but assume kdenlive is not using that.

Binho, thanks for info.
Sunab, yes deleting the kdenliverc in ~/.kde/share/config did the trick, old settings conflict then I guess, one to remember, thank you and thanks for your consistent and reliable PPA it makes access to kdenlive svn for Ubuntu based distro users so easy. :-)