I recently installed Ubuntu 13.10. And for some reason I am unable to download any plugin automatically. I never had this problem before. Here is an image what Rhythmbox or the default video player says while downloading plugins. Any help will be appreciated.
This is probably because you have not installed any codec for playing them.
For solving that, just install ubuntu-restricted-extras using the terminal. Press Ctrl+Alt+T to open the terminal and run the command:
sudo apt-get install ubuntu-restricted-extras
You can also do the same by searching for ubuntu-restricted-extras on Ubuntu Software Center and install it.
ubuntu-restricted-extras is a meta-package and other dependencies, like gstreamer0.10-ffmpeg, gstreamer0.10-fluendo-mp3, gstreamer0.10-pitfdll, gstreamer0.10-plugins-bad, gstreamer0.10-plugins-ugly, gstreamer0.10-plugins-bad-multiverse, gstreamer0.10-plugins-ugly-multiverse, icedtea6-plugin, libavcodec-extra-52, libmp4v2-0, ttf-mscorefonts-installer, unrar, are useful too.
