i had this problem and found an easy and cheap solution to the problem, its a common fault with these handsets which sony will charge a small fortune to repair when you can quite easily do it yourself.
If you have skype then you can contact me there where i will talk you through what needs to be done.
SKYPE NAME - dai262002
FACEBOOK - david w phillips
feel free to contact me anytime.
DAVE, October 2010
