iTunes won't recognise my play buttons

hi, my problem is that for iTunes, my f7-f9 keys won't work to play, go back or forward. they seem to work in every other app but itunes. and i used to be able to be browsing the web and press play/pause to stop my itunes music, but i now cannot. please help me, it is very irritating.

System Preferences/Keyboard
Make sure "Use all F1, F2, etc. keys as standard function keys" is not checked.