Car having trouble unlocking. Is it an actuator problem?

Car doors won't unlock with the
remote but has no problem locking.
Also one day when I tried unlocking
from inside the car using the car
doors it would lock and then unlock
right away. Haven't had that problem
again though but read it may be a
sign that the actuator is going bad. I
also noticed when after I park and
turn off the engine, when all the
doors unlock the rear door on the
behind the drivers side makes a loud
sound when the doors unlock. I had
this problem for weeks now but
sometimes I won't have problems
unlocking with the key. Just recently
it has been getting worse and not
unlocking at all. Any ideas?