Volume and FF keys not work on wireless keyboard iPhone

I replaced a wireless keyboard for my iMac today, and just noticed tonight that when I try to adjust the volume UP, it sends me to widgets, and when I try to adjust the volume DOWN, it dims the desktop behind my open window.
Ive tried checking, and unchecking, the box in Preferences>Keyboard>Use all F1, F2, etc. as standard function keys. Ive also gone to keyboard shortcuts and disabled F7 to F12. But no volume or rewind/ff etc.
How do I get my volume and rw/ff keys back? Thanks!
iMac8,1 2.8 GHz Mac OS X (10.5.8) compact wireless keyboard 2 batteries