white screen Help Please

[myp2]

Hi , my iphone 3g has had the white frozen screen several times now. It wont turn off unless holding both buttons down.(home/off). Some times it will recover by itself after awhile, have even left it over night and its come good.
Have had to do a full restore and jailbreak a few times. Can anyone please suggest something , I'm facing another full restore and jailbreak again.
There is nothing that triggers the white screen ,it just happens.

iphone phone 3g 4.2.1
Thanks in advance

ps even a link that may help????

SOLVED IT!!
after trying nearly everything listed on the web strange enough I got it going.
put it into dfu mode to boot and held the top right corner screen when apple logo started.
The logo sat doin nothing for 1 min. or so, decided to plug it into laptop and itunes finally picked it up and screen returned to normal. All well again till next time