I just played a file on my system and I did get subtitles downloaded. Is this how most people are getting them? Or is their some menu buried somewhere that the plugin creates?
If you are having a problem with one particular file or a set of files, while other files work, then you'd have to get me that info. You can PM me. I'll need to get the hash for the file.
The error means that the plugin had found a set of subtitles and was in the process of downloading them, but the OpenSubtitles server responded incorrectly. At least, it's incorrect according to the spec on their web site.
I really like the idea of the plugin, but I don't think it's much use to me. The APIs don't make it easy to get the foreign-only (non-english) parts. I'll see what I can do to help, however.
-tm