I believe that Lansweeper 5 may have a limit on the number of groups a user can be a member of.
Our organization uses AD groups for just about everything under the sun... My AD user is a member of several hundred groups, and the Website Access page only lists 61.
I have followed the instructions, and added users into AD groups and added those groups into the various Web Roles. However, whenever I do that I get locked out of the site altogether.