I have started experiencing that exact same error about 10 minutes ago. It was working fine, like yours.
This also happened to me a few weeks ago, but I just kept restarting MoW and eventually it worked. It doesn't seem to be working this time, however.
From what I managed to see for the few seconds I was in the MP lobby, everyones rank showed 0 with no rank symbol. Servers seemed to update fine.
Since neither of us modified anything i'm assuming it's Gamespy or something. I would also appreciate help
EDIT: It's working now, even though I did not do anything. I guess you have to just keep trying every few minutes.