Linuxconf validate the permissions bits of various key files and directories. Its resources file for redhat suggest roor,root,0400 for /etc/shadow. It seems the various utilities like usermod and friends set it back to 0600. I guess the resource file for linuxconf should be fixed to 0600 so it stops signaling this difference everytime you quit from Linuxconf.
*** This bug has been marked as a duplicate of 16212 ***