Restore previous session not working

[AN]

===>   Registering installation for firefox-nightly-27.0.151144,1
Installing firefox-nightly-27.0.151144,1... done


After a recent upgrade to firefox-nightly-27.0.151144,1 the menu option 
"Restore Previous Session" under the History menu is not available.  Has 
anyone else seen this behavior?  Is there a way to restore it?

I tried opening several windows with tabs, and exiting and then restarting 
the same way I always have but now I am unable to restore my previous 
session.  This is a major loss of functionality.  I would appreciate any 
feedback.  Thanks in advance.