Problem with my Microsoft Digital Media Pro keyboard

I hope it's the right section.

When my new keyboard just arrived, I installed it succesfully (with the provided drivers on the CD), and it worked very good.
I could press the music buttons ( Play/Pause, Stop, Previous track and Next track) just fine when my musicplayer wasn't active.
Like I was browsing in Mozilla Firefox, I heard a song and I didn't like it, I just pressed the Next track button, and the next track started.

But now, a couple of weeks later (I haven't did anything to the drivers or so in that time, the only thing I did was change the favorites and the F5 function), those music buttons don't work anymore when I'm in another application then my music player.
I haven't changed anything to my music player.

I've tried setting the buttons to their default functions and I've went to the Software download site of Microsoft and I've updated my drivers there.
But still, they don't work....

That's why I want to know if anyone else knows the solution to this problem