"You have an umlaut on your keyboard?"
I had one on mine once but the techie at the office said to use "Blow Off Duster" and it would remove it without harming the equipment. Caution, don't use it in a closed room, keep the door or window open. Thought I'd just pass that along.
Window open is an absolute necessity.
Never know when an umlaut will blow right past you without so much as a "howdy-do!"