Is my MacBook Air's trackpad broken?
Is it possible something got stuck or is otherwise jamming the trackpad?  Best bet may be to have genius bar take a look.  

On older macbooks there was an physical adjustment you could make on the trackpack (open the case, remove some stuff, adjust screw).  And we had a problem with the battery swelling which caused the trackpad to stop working (essentially prevented the "click" action, as it was pushing the trackpad up).