I've upgraded my Toshiba Portege R500 from Ubuntu 10.04 LTS to 12.04 LTS this weekend. The new system works smoothly, but if it enters the sleep mode, that is, if my laptop idles more than 15 minutes, the screen goes dim and turn to dark, and cannot wake up anymore. I've tried to press the Ctrl-Alt-F? and other keys, nothing works, the keyboard hangs. The mouse/keypad cannot work, either. The only workable key is the 'power'. If I encounter this problem, the only way I can do is to press the 'power' more than 3 second, and turn my laptop off... It's totally inconvenience.
In general, the hanging situation appears if the computer idles awhile and enters the sleep mode. That is, both the login screen and the working environment after login into the system, have the same problem.
Anyone could help me to fix this problem?