Facebook videos don't play with IE9 & Flash Player

To downgrade Flash, first follow the following steps for uninstalling version 11.3:

1. Download the official uninstaller.

2. Close all browsers.

3. Execute the uninstaller.

4. Reboot your computer.

5. Delete the following files and folders (if they still exist):

   %windir%\SysWOW64\FlashPlayerCPLApp.cpl
   %windir%\SysWOW64\FlashPlayerApp.exe
   %windir%\SysWOW64\FlashPlayerInstaller.exe
   %windir%\SysWOW64\Macromed\Flash
   %appdata%\Adobe\Flash Player
   %appdata%\Macromedia\Flash Player
   

6. Visit Archived Flash Player versions and download version 11.2 or lower.

7. Unzip the downloaded archive.

8. Run the installer.

9. When prompted, choose Notify me to install updates or Never check for updates to prevent Flash from updating automatically to 11.3 again.

Sources:

• How do I revert to a previous version of Flash Player?

• How do I do a clean install of Flash Player?