F150 Power Door Locks

I have a 2000 Ford F150 with a power door lock problem. About a month ago both power door locks started acting up. They would both actuate once, but would not actuate again, unless some time had passed. For instance, I would unlock the doors to go to the store, they would not immediately lock or unlock again when the lock or unlock button was pressed. After arriving at the store, the doors would both lock, but would not unlock or lock when the unlock or lock button was pressed. The same thing happens when I use the keyless remote. Any ideas?

I just installed a power door lock kit is a cherokee, man was that fun. When I had it wired and was testing it the actuators would take a two or three times to lock but would unlock on the first try. I found that there was a little binding and it was an easy fix. They are actually quite simple to work on and you should be able to understand it if you pull the panel off and check to make sure they are recieving power when you are trying to activate the locking feature. Or if the actuator needs replacing they are not very expensive.