Game Ending Glitch?

After the quest in which the blacksmith forges a new key out of the two halves, when I returned to Gunslinger Gulch, my hero was trapped on the ledge over the bandit base and unable to get down.

Thus, he's unable to go to the gate to unlock the door, and since there are no further quests that take me out of Gunslinger Gulch available (that I know of), the game is now unwinnable, unless someone else has any ideas?

Unfortunately, you will probably have to go back to your last save point, and start over from there.

This is why you need to Save periodically, in this and all similarly complex games. Loading so you can replay a segment can be massively annoying, but less so than starting an entire game over.