This issue I’m referring to, has already been around for quite some time now, and it’s usually occurs when you try to resize a video you’re watching to a full screen width upon the second time and above. Apparently this is not flash-player or even a specific web browser’s fault but a Gnome or GTK bug. (leave a comment if you know otherwise)
What happens is when you go out of a full screen mode and then try to go into it back again, the video usually just freezes although you can hear the playback still playing.
As an example, try to full-screen and out and then in again from the video on the following link: http://www.thedailyshow.com/full-episodes/thu-february-27-2014-kevin-roose
Did it work for you on the second time?
Unfortunately, there is no proper solution to solve this problem as of current, yet, don’t let it deter you, since the Linux community is full of many knowledgeable people and bug workarounds are one of the community specialties.
This solution was taken from Arch-Linux wiki, and is probably the most straightforward fix you can apply.
What you need to do is to install a package named devilspie (from your distro’s repo, or look for the source code), then, to make it work on Firefox, Create a folder called .devilspie inside your user directory, and a configuration file named flash-fullscreen-firefox.ds in there, with the following content:
(is (application_name) "plugin-container")
To make it work upon login to your system, open up “startup applications” by pressing Alt+F2 and type: gnome-session-properties > press the Add button and insert Devilspie inside the field name, and /usr/bin/devilspie inside the command field, like the image below shows > click Add.
If you’re not into going through all that just to get your flash player bug fixed, you can also opt for doing the following:
Upon the second and above time you’ll resize the flash player window, whenever it freezes, just go into activities overview and click on the “plugin-container” app you see there (see image on top).