Firstly 'tlmenu' is run as the database owner and is invariably therefore not 'root'; root or superuser access is required to be able to mount partitions. 'tlmenu' accomplishes this by running a program called 'realmount' which must have the setuid flag set on its permissions. If this is not the case then it will fail. The permissions are setup correctly on this program by running 'realstart' when first starting Reality and it's associated daemon processes and this must be run to correct the permissions.
Secondly, if the mount points, as defined in '/etc/vfstab' have had their mount options set to 'nosuid'; that is to say, you cannot execute setuid to mount these partitions. In order for Shadow Database to behave correctly you cannot specify this option and it must be removed from the '/etc/vfstab' file. See 'man vfstab' for further details.