I disabled the XFCE Session Manager when I last logged into XFCE, as it used to prompt for a new session to be named every time I logged into XFCE.
Now, I cannot login to XFCE. On trying to Login, the splash screen (with the mouse graphic) appears and then the desktop and panel appear very briefly (3-4 secs), and replaced by a blank black screen.

What can I do to re-enable 'Session Manager' ? I can boot via a 'Live CD' and make any necessary changes to system file(s)-but I don't know what XFCE file to alter ?