Product Firefox Release Channel release Version 49.0.1 Build ID 20160922113459 OS Windows 8.1 OS Version 6.3.9600 Signature: msmpeg2vdec.dll@0xdfe10 msmpeg2vdec.dll = Microsoft DTV-DVD Video Decoder ------------- Perform a System File Check to fix corrupted system files Win 7, 8, 10, Vista: https://support.microsoft.com/en-us/kb/929833 Win XP: https://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/system_file_checker.mspx?mfr=true See if there are updates for your graphics drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration