My WinFrotz Version is 1.17 (which is newer than the current version according to David Kinder's "deprecated" WinFrotz page
Annoyingly I can't access that old page to delete it: at least the version is correct here: http://davidkinder.co.uk/frotz.html
Yes, but unfortunately that link does not show up on the first page of search results when searching for "WinFrotz download".
But this could also be a problem with the personalized search results from Google.
There's no obvious reason why umlauts in the description would cause problems, but you could always try taking them out to test.
I tested that but it also didn't work.
There could be a bug in Windows Frotz here, or there could be something wrong with the generated XML in the Blorb file that iPhone Frotz is ignoring. If you email me the problem Blorb (my email address is in the Windows Frotz help file) I will have a look at it.
Since other blorbs did work (I just tried two random ones from http://mirrors.ibiblio.org/interactive-fiction/games/zcode/
I found some differences in the .iFiction file, but that also didn't help.
Last try: I'm sending the .zblorb via mail to see if there's anything wrong! (Althogh babel says it's ok!)