Take it to the dealer and get it checked out. Probably something simple. My 2000 GTS had every single component replaced on it and it still didn't work after a couple weeks. Finally traced it down to a bad seal on the lower hose. Replaced the entire hose (had to) and it worked perfectly ever since.
Sorry to hear of your woes, but it happens. There are bound to be failures of certain system on certain cars no matter how well they are built. Mercedes, BMW, Honda, Toyota - they all have a car or two that will have the A/C go out or something else. Get it checked and fixed by a reputable dealer and let us know what the fix was.
Chris