I would check first that all the screws are tight,take the cover plate off the edge of the door and tighten screws/try lock,they are a dead simple lock, a pin rotates and comes through a hole in the plate if it is not in line you can't remove key.Make sure the barrel hasn't moved from left to right stopping the pin from going through the slot,you have to remove these parts to fit a new one anyway,I would get the screwdriver out first and save some money and hassle,make sure when you try the lock with the door open that you STILL lift the handle up first as you do when it's closed.Screws come loose,try it,good luck.
Rich, December 2011