the autogroup mod, does NOT change any authorication code, only add/remove users from usergroups.
therefor if you have that kind of truble, it's more likely another mod installed, witch makes users permission/usergroup permission not work.
make shure you know exactly witch usergroups the user are in, and be shure to restrict the usergroups access prober.
PLEASE NOTE: the mod will not prevent users from staying in a usergroup, if you change the "post count" in group management.
to remove the "old" users after changeing the post count , you also need to "mark" the option "Delete/Update old users"
this way admin may deside if old users should be left in the group or alternativly be kicked out.
Earth should spin a litle slower, then there would be 28H/day