I have a 2005 Volvo XC70 wagon. On occasion the valet key will not turn the lock in the door. I am pretty certain it is not ice or freezing. It seems as if there is some "lock locking the lock"; it won't nudge at all! A couple times I have had to have someone bring me the remote key fob to get into my car. And then afterwards the valet key works.

Any explanation for this?