[OS X Emacs] changing input language

[Alex Hamann]

Hi,

I want to write a bilingual LaTeX document containing German and Greek letters. I use XeLaTeX for the job which allows me to directly input the Greek characters alongside the German ones. However, if I switch to the Greek keyboard in System Preferences Aquamacs only displays the very first letter I type in the correct Greek style and then just continues using latin characters for the subsequent letters (even though the Greek keyboard is still selected).
What is not right here?
Thanks in advance,

Alex