Recently we worked with our German teacher to help her figure out how to make German characters on the Mac like ö ä ü and ß. This involved using the International system preference and enabling the input menu. Here's a link to a tutorial on how to do it if you are interested in that.
Funny thing happened with that, however. As a result of working with the German teacher, I had my Mac switched to the German keyboard layout and mapping. I then left my office for some time to take care of some business on the second floor and returned only to find the screensaver asking for my password. Oops! Because I didn't switch back to the U.S. mapping prior to leaving my office, my keyboard was still in the German layout. The characters in my password that were now mis-mapped were not allowing me to authenticate to my account. What a nightmare!
Jeff Sankovich said, "Why don't you use fast user switching." He believed that by doing so you would then be using the keyboard layout of the other user and not your own to authenticate. It worked! I switched users and then used fast user switching to get back into my account and QUICKLY changed my keyboard mapping back to U.S.
Kudos to Jeff.