FYI, the default access is controlled by this line in the CMS file ;
PHP Code:
// Set default access
$userrole = ROLE_NOBODY ;
If you set that to ROLE_USER then they may be able to get in. The problem is that so will any other non banned usergroup (inc possibly guests, I can't test this atm). You *may* want to add lines for usergroups 1, 3 and 4 to the banned groups section (a few lines below the default).