Dialupadmin group problems

For some reason the edit user function of dialupadmin does not list all the groups available. The drop down box only shows the group the user is currently assigned to. In the add new user screen this box shows all groups and assigns them correctly. Looking at the page useredit.php I cannot discern why it is not showing all groups. Or allowing me to move the user from one group to another on the fly. Has anyone encountered this and fixed it or have the time to investigate it. As far as I can see the sql statement is correct to fill it with the group names. Regards Cory Robson