this can occur if the credentials that are being used for connecting to the Update Server do not have WSUS administrative privileges. Is this a possibility?
Feel free to email firstname.lastname@example.org and we can triage directly with you.
I have installed the trial version and am having the very same problem. The account I am using is an administrator on every server in the domain.
I have ensured that the "Do not allow storage of credentials...." setting in the Local Security Policy is disabled and there is no alias for the WSUS server.
I should probably add that I am trying to run the trial version from my XP workstation and connect to the WSUS server. I'm not permitted to install trial software on production servers
Please verify that the credential you have assigned to the WSUS server is a member of the WSUS Administrators or local Administrators group on the WSUS server.
Not a member of a group that is a member (as may be the case with Domain Admins being a member of local Administrators),
but that it is a direct member of the local group on the server.
If this still does not resolve your issue, please send an email to email@example.com and I will assist you further.