Using version 4.4 on Ubuntu with iPhone ZSubsonic app.
Noticed that on albums that contain filenames containing characters with umlaut, or accents, etc... that
1) the file won't play in native subsonic on the local PC ; and
2) trying to access the folder using Zsubsonic causes an "error reaching host" or something like that.
Renaming the files to eliminate the special characters completely fixed the problem.
I did not need to eliminate the characters contained in the mp3 tags.