hello RenaHo, can you try updating your graphics driver and see if this is making a difference?: http://support.amd.com/en-us/download/desktop?os=Windows%207%20-%2064

hello philipp, thanks for your answer. Unfortunately, the graphics driver cannot be installed, the catalyst install manager crashes as well.

does firefox launch into safemode when you press the shift key while the application is launching? if so disable hardware acceleration in the firefox menu ≡ > options > advanced > general and try to restart firefox normally again afterwards...

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) to see if that helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/