sudo 1.7.6p2 works as advertised ... but 1.8.2rc11 does not once compiled ...

User is in valid group in /etc/sudoers ... 

$ sudo su -

We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

Sorry, try again.
Sorry, try again.
Sorry, try again.
sudo: 3 incorrect password attempts

$ sudo -V
Sudo version 1.8.2rc11
Sudoers policy plugin version 1.8.2rc11
Sudoers file grammar version 40
Sudoers I/O plugin version 1.8.2rc11
...
# sudo -V
Sudo version 1.8.2rc11
Configure options: --prefix=/opt/phs --mandir=/opt/phs/man --infodir=/opt/phs/info --docdir=/opt/phs/doc/sudo-1.8.2rc11 --disable-nls
Sudoers policy plugin version 1.8.2rc11
Sudoers file grammar version 40

Sudoers path: /etc/sudoers
Authentication methods: 'aixauth'
Syslog facility if syslog is being used for logging: authpriv
Syslog priority to use when user authenticates successfully: notice
Syslog priority to use when user authenticates unsuccessfully: alert
Send mail if the user is not in sudoers
Use a separate timestamp for each user/tty combo
Lecture user the first time they run sudo
Require users to authenticate by default
Root may run sudo
Allow some information gathering to give useful error messages
Set the LOGNAME and USER environment variables
Length at which to wrap log file lines (0 for no wrap): 80
Authentication timestamp timeout: 5.0 minutes
Password prompt timeout: 5.0 minutes
Number of tries to enter a password: 3
Umask to use or 0777 to use user's: 022
Path to mail program: /usr/sbin/sendmail
Flags for mail program: -t
Address to send mail to: root
Subject line for mail messages: *** SECURITY information for %h ***
Incorrect password message: Sorry, try again.
Path to authentication timestamp dir: /var/lib/sudo
Default password prompt: Password:
Default user to run commands as: root
Path to the editor for use by visudo: /usr/bin/vi
When to require a password for 'list' pseudocommand: any
When to require a password for 'verify' pseudocommand: all
File descriptors >= 3 will be closed before executing a command
Reset the environment to a default set of variables
Environment variables to check for sanity:
        TERM
        LINGUAS
        LC_*
        LANGUAGE
        LANG
        COLORTERM
Environment variables to remove:
        RUBYOPT
        RUBYLIB
        PYTHONUSERBASE
        PYTHONINSPECT
        PYTHONPATH
        PYTHONHOME
        TMPPREFIX
        ZDOTDIR
        READNULLCMD
        NULLCMD
        FPATH
        PERL5DB
        PERL5OPT
        PERL5LIB
        PERLLIB
        PERLIO_DEBUG 
        JAVA_TOOL_OPTIONS
        SHELLOPTS
        GLOBIGNORE
        PS4
        BASH_ENV
        ENV
        TERMCAP
        TERMPATH
        TERMINFO_DIRS
        TERMINFO
        AUTHSTATE
        LIBPATH
        LDR_*
        _RLD*
        LD_*
        PATH_LOCALE
        NLSPATH
        HOSTALIASES
        RES_OPTIONS
        LOCALDOMAIN
        CDPATH
        IFS
Environment variables to preserve:
        ODMDIR
        XAUTHORIZATION
        XAUTHORITY
        TZ
        PS2
        PS1
        PATH
        LS_COLORS
        KRB5CCNAME
        HOSTNAME
        DISPLAY
        COLORS
Locale to use while parsing sudoers: C
Compress I/O logs using zlib
Directory in which to store input/output logs
File in which to store the input/output log
Add an entry to the utmp/utmpx file when allocating a pty

Local IP address and netmask pairs:
        x.x.x.x/255.255.255.0
        x.x.x.x/255.255.255.128

Sudoers I/O plugin version 1.8.2rc11

$ sudo-1.7.6 -V
Sudo version 1.7.6p2

$ sudo-1.7.6 su -

We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

Password:
root@host:~#