[PiTiVi] cannot compile development version. Stuck at step 0

Hi,

I'm trying to download and compile the development version of pitivi, 
because the current stable release crashes almost at every mouse click...

I guess I'm missing something very basic, but I'm following the online 
instructions step by step from here: 
http://wiki.pitivi.org/wiki/Building_with_GES

sudo apt-get install python-gtk2-dev
sudo apt-get build-dep pitivi python-gst0.10 gstreamer0.10 gnonlin

and I get:
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to find a source package for pitivi

What am I missing?

thanks
m.

------------------------------------------------------------------------------
This SF email is sponsosred by:
Try Windows Azure free for 90 days Click Here 
http://p.sf.net/sfu/sfd2d-msazure