thank you for taking care about this problem.
After you told me to send the log file, I checked the logfile. I think I localized the problem.
When it was needed to transcode, the PSM called an external program (ffmpeg) in the Java/osx folder. The ffmpeg started, and quitted as "no such file or directory" and quoted the entire directory path.
And that was the point when I got some lightbulb over my head
The avi files are on an external volume on my system, called "Raktár". As you see it contains a accentuated caharcter. I got curious that if I rename it to something not accentuated, what happens. And everything got working flawlessly.
I thint this is the main problem with subtitling --- definetely those users want subtitling, who speak a different language than english. And then the ffmpeg crashes since it can not understand these characters (uhm-uhm...), and many languages - other than english - have these letters, in filenames, and in volume names too.
After all I have to tell you, that I tried some media server apps for osx, and FAR the PS3 Media Server was the best to handle strange characters, many other softwares put some ' and " in filenames instead of using ó or ő letters --- unfortunately these happen often in my languege (Hungarian).
So I think that the widely usable solution would be to make ffmpeg able to handle these little letters