Cannot use alt+u umlauts with American keyboard

[mikulcak]

Hi,
unfortunately due to the Alt+u shortcut I cannot enter umlauts anymore (äüö). There's an explanation on how to enter them in the first place here: http://www.nthuleen.com/teach/misc/typingumlauts.html

I tried changing the keyboard shortcut as a User setting but that did not solve the problem, unfortunately.

Thank you very much!
Marcus