Sony Ericsson k850i - Screen goes black when pressing keys, but keys stay lit.?

[bassmanhales]

I've only just come across this problem with my phone. When i press keys on the pad, the screen will go black but the keys will stay lit. I cannot get the screen to come back on untill the lights have gone off. After i press a key again, the screen will come on, but on pressing another key, the screen will go black once again. The phone still works and is navigating (I tried to text when the screen was black and it worked) and i've only just recently updated it's software, about a month ago, so does anyone know a fix for this?

If there is a solution in which i could fix it myself without having to send it away or taking it into the shops, i would be more than happy.

Thanks.