Door Won't Lock With Key

[davintosh]

Ok, new problem today; I went to lock the X5 from outside using the key, and the key won't turn to the right to lock it. It turns to the left just fine, but not to the right.

We have two keys for the vehicle, but the battery only works in one of them, and recently it's been a little dodgy, only working once in a while, and only when very close to the vehicle. The other one has a dead battery, and I've had good intentions to replace it, but... Getting the thing to lock has suddenly become a problem.

Any thoughts on why the key lock won't turn?