Updated cinnamon then lost all access when trying to retrieve screensaver

After updating linux mint I lost the screensaver and when trying to get it working again, after reading online hints, I cannot get my computer to restart. I get the message: unable to launch "cinnamon-session-cinnamon" X session--- "cinnamon-session-cinnamon" not found; falling back to default session. When I click the ok button (which is the only choice) the screen goes blank. On startup, I am asked for my password to unlock before going to black. Any ideas on how I might recover in startup screens??