Key fob lights up, but remore control doesnt work?

[lurky]

Hi
I have a 2007 boxster and things are starting to go wrong one after another. I just replaced the plastic ball joins on the retractable top, and now the remote key fob stopped working. I replaced the battery in the key fob. Now the fob lights up when I press the buttons, but none of the remote control functionality works (lock, hood or trunk). So I think, but I'm not sure, that the problem is with the receiver in the car. The car's electric system seems to be okay, or at least there are no other apparent failure.
How would you go about confirming the problem? I only have one fob.
And is the RC receiver in the car a component that tends to fail and can it be replaced?