Cannot log in with CORRECT password
 

Here's one that will probably take an abolute Linux god to troubleshoot: Whenever I try to log in as any account in Red Hat 9 with the correct password, I get a popup box that says "Authentication failed."

If I try an incorrect password, it says "Incorrect username or password. Letters must be typed in the correct case. Please make sure the Caps Lock key is not enabled" below the login box.

I am sure that the password is right, because I booted in as root by passing the single parameter to the kernel from the bootloader, and I changed my root password and my user account to password (I made sure caps lock was off and typed it all out with one finger slowly to make sure there were no typos). Even in single-user mode, if I try to use SU (doesn't matter what username I give it), instead of prompting me for a password, it just says "incorrect password"

EDIT: Yes, it is my own fault. I made a bunch of changes to the system trying to get the bugger to authenticate to a Windows 2000 ISA server to get out to the internet, but there were a *lot* of changes, and I don't remember what all of them were, so I can't begin to guess at what I did to slaik login security up like this.

My guess is that it has somethis to do with somehting in "/etc/security" possibly access.conf - does that ring any bells?

You can comment everythig in access.conf out if there is anything uncommented.

I wonder if the above problem is at all related to my problem?

Under RedHat 9 I have had a look in /etc/security/access.conf which in default format is all commented out

# Disallow console logins to all but a few accounts.
#
#-:ALL EXCEPT wheel shutdown sync:LOCAL
#
# Disallow non-local logins to privileged accounts (group wheel).
#
#-:wheel:ALL EXCEPT LOCAL .win.tue.nl
#
# Some accounts are not allowed to login from anywhere:
#
#-:wsbscaro wsbsecr wsbspac wsbsym wscosor wstaiwde:ALL
#
# All other accounts are allowed to login from anywhere.

and my /etc/securetty lists all the normal ttys

console
vc/1
...
vc/11
tty1
...
tty11


I have no problem logging in as root, but whenever I want as root to su to a different user it always asks me for the password of the user. This behavior is different from RedHat 8 and earlier versions.

Why is su under root asking for passwords and how do I change it to the "normal" behavior?