I'm having a problem where I must not be understanding something.

I've installed the Enterprise Console and server on the same machine - an XP Pro machine dedicated to only running the Avast Console and Server. I can get in just fine with the "admin" initial password. I can pretty much do anything I need to do so far, scans, push installs, discover computers, etc. So far, so good. Then I signout and I can't sign back in.
I've done this twice. The first time after a clean install, and doing some work in the Console, I changed the administrator password. Later when I tried to log in, no password, old or new, worked. I tried resetting the administrator password with the instructions given on this forum and that appeared to process correctly, but I still could not get in. So I uninstalled everything - server, console, client, SQL Server, etc. Rebooted and started over.
This time around, I'm thinking, "not going to change the password - stay safe (if insecure!)". So I didn't. After doing some work, I log out. Now I can't log back in again. EXACT same problem. "unable to login as Aministrator or connection error".
Just now, I updated to the latest program based on the announcement in the forum yesterday. That went fine, but I still can't log in.
Since I've not changed any password, I'm guessing it's the "connection error". So EVERYTHING is running locally on this machine. What should I look at to enable this thing to connect (even though it already WAS successfully connected)?
Any help would be welcome.
Thanks!