Hi,
Since it says:
gnome-session: you're already running a session manager
it looks like you have a running X manager or at least some parts of it still in the memory. Will you please post the outputs from these commands?
echo $SESSION_MANAGER
and
ps -aef
You've told you've deleted files from the /etc/X11/tmp but the files are generally under /tmp
Cheers,
K.