I had a bunch of files and folders (website) i wanted to track in fossil. However i couldn't commit anything, because during the commit process right after "New version..." line i got the following error:

"fossil: manifest file (931) is malformed"

It turned out to be one of my files contained a german umlaut "ö" in the file name...as soon i renamed the file (removed the german umlaut), i could successfully commit.
Probably same error might appear with all other special german characters "öäüß".
The error message about a malformed manifest file is not very conclusive and does not give me any clue that the problem is not with the manifest file but with the characters in the filename of my files.