new user

hello

I am a freebsd new user , i already install freebsd 6.0.3 and then i use Csup update ports-tree and then use Csup
to safety update after reboot back to the login screen , when i input user name and password , it back to the login location , i use another user name that i create before ,I also reinstall again also like this why??? Anyone can teach me how to fix it , many thx^^

1.CsupPort Tree
#cd /usr/ports/net/csup
#make install clean

1-2.change port file (ports-supfile)
1-2-1.change ports-supfile
default host CHANGE_THIS.FreeBSD.org
change to--->default host cvsup.tw.freebsd.org
#rehash
#csup -L 2 ports-supfile <---------success update

1-2-2change /etc/make.conf <---------i can see this file but
change /etc/make.conf
SUP_UPDATE=yes <---------can't see this?
SUP=/usr/local/bin/csup
SUPFLAGS=-L 2
SUPHOST=cvsup.tw.FreeBSD.org
PORTSSUPFILE=/usr/share/examples/cvsup/ports-supfile
#cd /usr/ports
#make update

  1. Csup safety update
    #cd /usr/share/examples/cvsup/
    #vi stable-supfile
    *default host=CHANGE_THIS.FreeBSD.org
    change to-->*default host=cvsup.tw.freebsd.org

*default release=cvs tag=RELENG_6
change to-->*default release=cvs tag=RELENG_6_0

#cd /usr/share/examples/cvsup
#rehash
#csup -L 2 stable-supfile <---------success update

#cd /usr/src
#make buildworld kernel
#reboot <----HERE!!! when i reboot that is what i say
#make installworld
#reboot

following this guide helped me a lot when i was new to freebsd.
Howto: Mergemaster and Make World.

So, now you can't log in to the computer at all?