Text_Highlighter problem

Hi! I'm at the moment trying to get your PEAR package Text_Highlighter running for a Midgard frontend to PHP code. So far, it's working really well, but unfortunately, when I enter non-ASCII characters in the code I want to parse, the blocks and regions matching defined in the XMl file is not longer working correctly. When I enter for example ä outside of any tags or elements, it is displayed normally with the default style. When I enter the same letter inside, for example, a quoted region like this: 'ä', teh Text_highlighter seems to mess up the charset an treats it as two characters. From what I can tell, all content is encoded in UTF-8, but I don't know if that has anything to do with it. If you have any ideas where to look for the solution of this, I'd be very grateful. Bye, Andreas