Not Authorized Error when adding users on the Back

Get what looks to be a Javascript dialog box centered on a gray screen that says 'not authorized'

Repeat by: logging in to back side of the site as SuperAdmin, components->Community Builder->User Management and try to add a new user.

CB 1.7.1
Joomla 1.5.25
Ran all the tools to check the databases.

I'm logged in as a Super Admin
Other Super Admins report same issue, logged in to the admin side, trying to add a new user. The ajax email and user name checking say both are valid.
Tried it with and without the mootools upgrade plugin enabled, same results.
Nothing in the error log.
Any help would be appreciated.

Brent

Does the not authorized happen directly after clicking the Save button? This can be a result of a Joomla system or Joomla user plugin conflicting. It can also happen if a 3rd party CB plugin is conflicting. Please disable non-core CB plugins 1 by 1 until resolved, if not repeat with non-core Joomla system plugins until resolved, if not repeat with non-core Joomla user plugins.

I have exactly sames problems.

Did you find some solution?

Thank you

Joomla 1.5.23
CB 1.8.

Please read my above reply and follow the debug steps.