Firefox session manager fail

[rhia_starsong]

Hi, I am having trouble with version 20.0 of Firefox.  I have session manager as an add-on, with the options to restore my windows/tabs from last time in both Firefox preferences as well as session manager.  However, in the last few days, session manager no longer seems to function: it is not creating backups, when I restart my browser it just brings up the homepage and not my old tabs, and it doesn't have my closed tabs list anymore (it acts as if I haven't closed any tabs at all).

Does anyone have any ideas on how to fix this?  The restore session function is a major reason I use Firefox!

I am running Ubuntu 12.04LTS.  Thanks!