If you're trying to register, you may be experiencing an issue where you get an error message saying that your User Name and/or Display Name is already taken. In most cases, this is not the case. In addition, if there is already a user on the same computer, the screen may override what you type in with the earlier username.

This blocking issue has been escalated to our provider.

Since the site has just undergone an upgrade, this would seem to be just one of the software adjustments that needs fixing before the whole process is complete. Correct?

Yes. I expect that we'll be working to resolve the various upgrade issues over the next week or so, but this one is the most urgent.