Nokia

Hello. I recently bought a Nokia 6170 phone and it seems to have a software problem, or so I think. Randomly the mainscreen blocks displaing only the clock on a white background. Also the buttons ''Menu'', ''go to'' and ''names'' can be seen on the lower part of the sceen. If a close phone, the other screen shows the clock in the same way. The only thing left to do is to restart the phone. I wonder if anybody else had this problem because I searched and did not find any topics regarding my problem. Thanks.