there was a common fault with the drivers door latch back in the day. the problem being that the latch mech would jam, caused by a number of reasons. can you get into the other side of the cab, if so take the door panel off and manually operate the lock. You may find a few bits of plastic in the well at the botton of the door, or find the rod which connects the lock to the latch has come off (why the key don't work).
if you can get it open then great. remove the latch assembly and check, check for free movement and a strong latching. if the plastic which covers the latch 'hook' is loose/split its possible to remove it with sharp knife. if fault its a trip to dealers or breakers.
pj, November 2009
