Have you tried that old standby of unplugging it form the mains for several minutes then plugging back in? Sometimes works if things have locked up.
If that doesn't work then could be anything. Usual suspect is a dodgy power supply. Component failure in the PSU, especially electrolytic capacitors, can cause all sorts of problems. Depending on how competent you are with screwdriver and soldering iron you may be able to identify the failed parts and replace them. That is assuming it is possible to easily identify the failed part in the first place.
Getting someone to repair it for you may cost more than it is worth however.