E763 'Word Characters' differ de.utf-8.spl

Hello to everybody,

since a couple of month I have a problem with my de.utf-8.spl. Everytime I start vim, it reports:

Fehler beim Ausführen von "/home/mpw/.vim/spell/de.utf-8.spl":
E763: 'Word Characters' unterscheiden sich zwischen Rechtschreibwörterbüchern
Betätigen Sie die EINGABETASTE oder geben Sie einen Befehl ein

Translation:
Error during execution of ~/.vim/spell/de.utf-8.spl
E763 'Word Characters' differ between the two spell dictionaries
Press key to continue

Which "two" dictonaries"? I have only one.

I replaced the the files:

de.utf-8.spl
de.utf-8.sug

several times with the uptodate versions from here:
http://ftp.vim.org/vim/runtime/spell/de.utf-8.spl
http://ftp.vim.org/vim/runtime/spell/de.utf-8.sug

The spell check works. I just want to get rid of this warning message.

Thanks for reading.

Greetings from Germany
Matthias Walther