iphone says connect to itunes but when connected nothing happens

Hi;

I am having a problem with my iphone. It was working fine yesterday and then just seemed to power off.

I plugged it into charge (wall socket) and after a while it was fully charged and the screen showed the "connect to itunes" logo.

I then unplugged it from the wall socket and attached it to USB on computer and opened itunes.

Then nothing happened, the phone screen is blank and not recognised in itunes or on the computer as a recognised device?

Anyone else seen this problem or know how to resolve it?

Thanks