Wow. I created a simple group. I couldn't add myself to the group because I'm already the site Admin so it wasn't possible or necessary. I then activated UAM to this group on a couple of page. Each time I clicked update after protecting it with UAM on that page it gave me the error message "You have no rights to access this content." Huh? I'm the Admin. I should have access to everything. Also when I went to the page on the client side I could see all the page content (makes sense since I'm the Admin) but when I click edit link on the page I get the same error message "You have no rights to access this content." Huh again? This is all not good at all but even worse is that this page that I activated UAM on no longer even shows up in my list of Pages. The page is visible on the client side but is essentially now frozen permanently, uneditable at all and invisible from within the WordPress. Can't edit it, can't even see it in the list of pages - so I obviously can't remove the UAM protection from it.
Another separate issue is that I did add another few users to this group I had created but now that part of their user profile is grayed out and unchangeable any more. In other words, after I added a user to a group and clicked save, it was apparently a permanent state that could never be removed because it still shows him being part of that group, but it's grayed out and unclickable so I'm completely unable to change or remove him from that group.
The only thing I can do to gain editing access to my pages again (even though I was already the Admin) was to reset UAM and then deactivate. Shame though because I'd really like this plug in to work to create a members area.