Generally I don't power off my machine at the end of the day or for that matter anytime unless there are updates that prompt me to restart. Also I leave firefox ON with 10-15 tabs! So the system is ON for weeks sometimes even a month or two! Ofcourse some of the processes start getting slower and slower. especially Firefox. But then all I need to fix that is to restart Firefox.
But in the last 6 months or so I have been encountering this weird problem.
when I come to work the next day...many times I couldn't get to the login dialog screen, no matter how hard I tried with the mouse or keyboard. Seemed like the gnome screen saver had gone into the weeds! The machine was ON and everything was running. The solution to this is to login through a command line session CTRL-ALT-F6 and kill the gnome-screen saver process. I used top utility to find the process id (look for gnome-screensaver in the command column) and also kill it. and then try ALT-F7 and everything is fine.