There is a new build that should fix without any mucking around
(if one edited the upstart file then set back
gnome-panel (1:3.6.2-0ubuntu13) saucy; urgency=low

* Drop bin/gnome-session-flashback as it wasn't consistently used and
caused problems with upstart user sessions. (LP: #1217991)
* Add aliases for gnome-fallback to gnome-flashback and
gnome-fallback-compiz to gnome-flashback-compiz.
Here I just purged gnome-session-flashback then re-installed with new one, seems ok