Murphy's Corollary

I have an unusual problem. My master door lock and keyless entry UNLOCK all 4 doors just fine. The problem is that neither will LOCK any of the doors. I've checked the actuator, it works, the lights flash, there is a clicking noise (sometimes) like it's trying to lock the doors, but nothing happens. It used to work if you pressed the lock 10-15 times and crossed your fingers. Now it won't lock the doors at all and I have to manually lock them individually. Again, unlocking is no problem. I've also checked the fuse. Any suggestions?

Murphy's Corollary

Bubmping up; still looking for an answer please.