Hi tnygard,
Had the same thing happen to me, scratched and prodded for hours until I worked it out.
If you can see the top end of the lock through the window cavity in the door (See the picture to work out on how to unlock the door.
If the plastic dust cover is still fitted you’re going to have to remove it. Can’t help you there.
The reason for it locking up is the rod that connects the key barrel to the lock has come out of adjustment. IMO
(http://i78.photobucket.com/albums/j96/nzank/Misc/doorlock3.jpg)