Something like that happened to me when I first got my Legacy. I took it back to the dealer and they hooked it up to the A/C machine, and after that it worked fine, like the system just needed to be primed. So if I were you I would make an appointment with your dealer's service department as soon as possible to get that looked at.
FYI, I haven't heard of this happening to anybody else, so it's apparently an extremely rare occurance.