I am using Ubuntu 13.04 x64 (with latest updates) on my Dell Studio 17.
Plugged into my charger, I open up a YouTube video in Firefox 22 in full-screen, which is using Adobe Flash.
After about 10 minutes, I hear a dialogue box opening sound; and only the mouse pointer is moveable.
I cannot switch terminals (to tty6 or whatever); and have to hard shutdown.
How do I fix this?