Hmm... the German path names shouldn't be an issue, we use a system function to find the localized name of the "Program Files" directory. Did you try putting the files in the root directory of the whole system (\\)? And are you sure these \Programme, \Pleco, \Program Files, etc folders were being created in the root directory rather than in your My Documents folder? (My Documents is usually what appears first when you open up the Mobile Device icon, you have to open up "My Windows Mobile-based Device" to get the root directory)
We should have the first trial version of our automated Pocket PC installer up here in a few days (already basically works, just have to configure it with the right files) so that might fix this if you can't get it working any other way.