Comment 2 for bug 686851

On the same layer: do you drag them onto each other, or one besides another?

If the former, then it's probably https://bugzilla.gnome.org/show_bug.cgi?id=632414

If the latter, could you provide the gzipped output of
PITIVI_DEBUG=*:5 GST_DEBUG=2 /usr/bin/pitivi > debug.log 2>&1

If it's a segfault (I can't really tell because you haven't said so), make sure you have

python-dbg python-gtk2-dbg libgtk2.0-0-dbg python-gst0.10-dbg gstreamer0.10-gnonlin-dbg *gstreamer0.10*-dbg libglib2.0-0-dbg python-cairo-dbg

...installed, then run:

"gdb python"

...then, at the gdb prompt, type "run /usr/bin/pitivi"

Make it crash, then enter:
"bt full"

Scroll as much as needed, save the output to a text file and and attach it here.