Have you changed the username/password you use here on the forums?  Whatever you use to log in here is what you need to log into Impulse.

-Exile Dark

OK.  thanks.  The problem seemed to be a change to my email address, so the login from Impulse on my computer was in the old email address -- but the change to the email address was about a year ago and I have updated several times since then, including buying Diplomacy, without a problem.  So I still don't get it, but once I knew the issue was with my log-ion I figured it out.