lucy24 - 6:15 pm on Apr 19, 2011 (gmt 0)
Urk! Those are hex FFFF and FFFD, where the latter is the utf-8 "replacement character" meaning "I can't deal with this". As it happens, the characters ü and ß both occupy locations that are permitted in Latin-1 but not in UTF-8, in the 0080-009F range. So it sounds as if you have managed to turn the original problem on its head :-) That is, first you had UTF-8 characters being interpreted as Latin-1, and now you have Latin-1 characters being interpreted as UTF-8.
What is the encoding of your original file-- the one on your computer that you're looking at right now? If the file itself is in Latin-1, changing the HTML header to say UTF-8 (or vice versa, or any other permutation of encodings) will not change the text, it will simply make it display incorrectly. See what happens if you leave everything exactly the way it is, but change the "UTF-8" piece to "ISO-Latin-1" (or 8859-1 if that's what the software expects).
Disclaimer: I do not speak php, though I do know German ;-)