Every time I rebooted or logged out of my Ubuntu virtual machine, my keyboard layout would switch to "Germany Eliminate dead keys" ("Deu"). Removing the offending layout from the keyboard manager seemed to work, but the problem would reappear the next time I logged in!
Ultimately, the solution that worked for me was:
Open System | Preferences | Keyboard
Select the Layouts tab
Select the German keyboard layout and click 'Remove'
Click "Apply System-Wide" (critical step)
Close and reboot (critical step)
For some reason, the reboot was required. Merely logging out and back in resulted in the old behavior.
If you wish to keep the other keyboard layout(s), make sure that the correct language is selected at the bottom of the login screen. If you don't have a login screen, turn it on by selecting System | Administration | Login Screen, click Unlock, select "Show the screen for choosing who will log in," and log out.