EVERYONE has had that problem, and the fix is commonplace... a quick "search" under troubleshooting for "defrost only" or "no panel a/c" or the like, would have turned up that your AC operates on the presence of vacuum or no-vacuum. The default location to route air is the defrost panel, and that is when there is no vacuum applied.
You likely lost your vacuum connection, and therefore are experiencing this. The search would ALSO have turned up that you can check the vacuum dash pot from the passenger side, behind the radio area (look between the firewall and the console, for the hard plastic vacuum tubes. One likely fell off of the pot itself.
Ray
