Hi, I have had the same problem, but solved it by installing some cb-plugins new.
A reversion of the tab access didn't work, because they have been comletely lost.
In my case the article-tab and the uddeim-inbox-tab were affected.
When I installed the new version of uddeim 2.5 beta with related cb-plugins they suddenly reemerged together with the restricted access levels set before.
May be its a bug of uddeim 2.4 beta in combination with custom user-groups in J1.6?
Hope, any update like this will work for you, too.
By the way: be careful with installation of cb, don't use joomla standard login component parallel, always set up the cb profile menu link to public and activate it...
Hey Nick - see you are online so I am posting direct to you.
I have the same problem with items being dropped when you change the [access] field. It just drops out of site. I PAID for the advanced membership because it said that there was COMPLETE documentation - it is NOT complete - there are so many features of the CB product that are not discussed, especially the additional plugins that come with the ADVANCED membership.
This problem has been around for two weeks and the only response that we get is "Revert tab access to previous group I guess."
nant