White screen on my e900?

I recieved all lot of calls all afternoon,then i filp my phone up and it went all white, i thought i was jus worn out because of the calls and had jus gave up! That night i took the battery out and put the phone on the radiator(heard a story), next morning put the battery in and the fone started workin for about 5 mins then went all white again. why? plz help cuz i dont wanna fork out 4 a new screen.