Adobe Digital Editions Connection Error During Authorization (Mac)

When I try to authorize my computer I get a popup: "Connection Error.  Digital Editions could not connect to the activation server.  Please make sure you are connected to the internet."

I have a working internet connection.

I have already tried uninstalling and re-installing with my firewall off, checked that my computer wasn't authorized previously (it wasn't), and tried using an older version (1.72, same error).  I also tried authorizing with and without an ID, and both returned the same message.

The file I'm trying to open is .acsm. 

Please help!  I'll have to spend hundreds of dollars on textbooks if I can't get them from my school's online library.