Cannot connect to authentication OR fulfillment server

I've used ADE for over a year without any problems. Yesterday, it suddenly refused to connect to the authorization server. I waited a day to see if it was a server problem. Tonight, same issue.

I read all the forum advice, and tried everything suggested: I uninstalled ADE, reinstalled it, same problem. I de-authorized ADE, uninstalled it, installed v. 1.7.2, got the error message that it couldn't connect to the authorization server. Uninstalled v.1.7.2, reinstalled v.2.0, same problem.

I tried all these steps twice. And yes, I checked my firewall and cleared my cache.

If anybody has any other ideas, I'd love to hear them!