Multimedia keys gone

Hi.

I was working with an apple keyboard without problems. Bur suddenly, multimedia keys dont work. No with amarok, no with Banshee or Clementine. Work volume keys, but not play/pause, fordward and retry.

I have tried to configure it at Config>Keyboard, in shotcuts, but after do it, if I clic over one of them, just shows the icon of no multimedia sources on.

Some idea about what can I do? Thanks in advance.