Minimise, maximise and close buttons do not work whilst Firefox is the active window.
When Firefox is active, the aforementioned buttons do not work. The same occurs for buttons within Youtube videos. The buttons do not enter a 'hoovered over' state either.
In order to click any, I must click the taskbar then they become available once the window is no longer active. This occurs for any Firefox related window (Downloads, About Firefox etc.) but no other programs on my PC.
I have tried disabling all addons, starting in Firefox Safe Mode, and uninstalling and updating to 17.0 then repeating those steps.
PROBLEM RESOLVED, but not understood. I opened my work webmail bookmark, which opens in a new window, and suddenly everything had resolved itself.