Wireless Keyboard not responding at all

Hi everybody, so recently i bought a wireless keyboard for my mac, and when i tried to use, it only worked the function keys. (volume, next song) and the alphanumerical didn't work, I already tried to use it with my brothers mac, and it worked normally but in my mac i didn't

Specifications of my mac
Mac Os X 10.5.5
2.16.
4Gb Ram

Another thing my macbook its one of the first mac, i doesn't have in my keyboard the functions of next song

Thanks

Hi, yes the first time I used it I paired it with my macbook.. and it didn't work only the function buttons and the tab button. Then i thought that maybe was the keyboard and my brother has also a macbook so i paired with his, and it work fine.

Thanks