Central locking faulty?

Near side front door locked and won't open. Replaced central locking solenoid and seemed to work for about an hour then same problem happened again. Took door pannel off and can see that when door handle is pulled the cable is working fine but the door still won't open. When fob is pressed it sounds like it locks and un-locks but still door won't open. Can anyone help??

S.C.F.C Jim
March 2009