Can you tell us if you used any tool firs of your last reboot ??
I think you have modified /etc/ttys file.
Here is written wiche shell mac os x has to launch on boot.
so ... if you want we can try to investigate the problem...
boot your mac and make a textual login, at prompt type
less /etc/ttys
this command will on-screen-print /etc/ttys file.
near the top of the file you should find two lines containing the word 'console'
in os 10.4 is something similar:
# @(#)ttys 5.2 (Berkeley) 6/10/93
#
# name getty type status comments
#
# To secure single-user mode, enable Open Firmware password protection.
#
http://www.apple.com/downloads/macosx/apple/openfirmwarepassword.html
#
http://docs.info.apple.com/article.html?artnum=120095
#
#console "/usr/libexec/getty std.57600" vt100 on secure
console "/System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow" vt100 on secure onoption="/usr/libexec/getty std.9600" /Contents/MacOS/loginwindow" vt100 on secure onoption="/usr/libexec/getty std.9600"
(i can't remember 10.2.x format and my mac does't boot with it.)
(anyway it should be similar...)
Well ...
one of two console word starting lines sould be commented (with # symbol)
the commented line for commandline login should be console "/System/Library/CoreServices/loginwindow.app/
leaving uncommented the first.
so ... please post results.
looking forward to hearing from you