Hi! I'm on 2.2 in my 2G 16GB iPhone. Some times the screen turns black and don't response to homescreen button or to power button. But if i plug in the USB to the charger or the PC the screen turns back it normal and the iPhone response normaly. Other wise i have to reboot the iPhone presing down the home and power button and then is normal again. I uses QuickPwn to jailbreak and unlock. This happened to me since in have on 2.x firmware. Someone Know what the matters with the iPhone? Thanks a lot, i looked the forum but did not find one case similar to my problem.

Best is to restore the phone and jailbreak/activate it again.
sort of like a windows reinstall :-)
When done, setup your phone as new phone in itunes. Don't restore a backup to it

Thank you for your reply. If i will do it mi phone contacs will lose it? I can back up all the other data but the contacs info don't know it.. Do you know how i can do that back up?