Thanks for the answer.
I just tried that. I opened the LFM file with Notepad++ and hit "Convert to UTF-8". I tried UTF-8, UTF-8 with BOM and ANSI. Always the same result, the Lazarus-IDE shows the form correctly, as soon as it is compiled the running application shows "?". Any other ideas?
Would it be of help to attach the LFM-file to the posting?