LG P920 Guide De L'utilisateur page 461

Message
Hang up or freeze
Possible causes
Intermittent software
problem
Possible Corrective Measures
Remove and re-insert battery.
Turn on the phone.
If the phone is locked and does not work,
press and hold the Power/Lock key for
10 seconds to turn it off. Then, press the
Power/Lock key again for  seconds to reboot
the phone.
Try to do a software update service via the
website.
10