In the Keyboard and Mouse section, under the Keyboard Tab, check the box that says "Use all F1, F2, etc. keys as function keys" Then you just press fn to use the hardware functionality. Man, you have been having more issues with your iMac, the keyboard, and the software you are running... just wow, not saying anything negatively, just you know wow. However, next issue that you might have, i would say drop it in an existing thread instead of starting another one.