Unfortunately, this doesn't seem to be a matter of just the latest update. I seem to be current. If I click on history, it shows that I've got beta 3.0a installed.
However, whenever I go to Multiplayer/Internet, I can enter my Impulse login info, and I get the message you mentioned. I've tried clicking Create Account, but it does nothing. I've also right clicked on Demigod in Impulse and tried "Re-Activate". But the game simply isn't letting me in.
-Tom
EDIT: Actually, it looks like it is a matter of not being updated. I finally got Impulse to tell me there was an update available, but only by trying a right click called "Verify Installation". Before I did that, it seemed like Impulse had no idea I needed to update.