emerge newbie, I had the exact same problem since last week after I did an 'emerge world' and I will tell you that it IS the /etc/login.defs update that corrected your problem.
I thought it was before when I had commented the offending lines out and the erros went away, but I was told by a friend that I should try to fix the problem another way if those lines where suppose to be there. While trying to figure it out today I:
1) ran 'etc-update' in shell
2) scrolled through the list of updates I had on my system
3) exited the menu (-1)
4) cp /etc/login.defs /etc/login.defs.original as a back up.
5) ran 'etc-update' again and went through the displayed instructions of doing a complete replace of the origional with the update.
I would like to thank <a href='http://forums.gentoo.org/viewtopic.php?p=144774'>rac</a> for pointing me to your string here. Now we can help another newbie like ourselves.

