On my Fedora 20 setup, I cannot load any video into gnome-subtitles.  I tried the following:
1) Install the official package using: # yum install gnome-subtitles
2) $ gnome-subtitles
3) Video -> Open
4) The program suddenly crashes.
5) In the terminal, I see the following:

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$ gnome-subtitles 
Got 7 languages.
Got video duration: 00:05:45.3120000

(gnome-subtitles:1522): Gdk-ERROR **: The program 'gnome-subtitles' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
  (Details: serial 32 error_code 8 request_code 148 minor_code 13)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
Trace/breakpoint trap (core dumped)
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I tried XVid4, WebM and OGG videos, but none worked.

I also tried reinstalling gnome-subtitles and gstreamer, but this didn't solve the issue.

Please also note that totem works just fine.