su strange behaviour

[Marcel Reese]

Dear Reader!

I recently had to change user mare's user id. This has also been done 
for all his files's owner tags. After this su doesn't work properly 
anymore for any user except for root. It accepts correct passwords and 
waits after typing wrong passwords, but it never logs in the specified 
user. There are no error messages. I would appreciate very much to know 
how the reseason of this problem and certainly a solution. Here an 
example what can happen: ('Password:' if no error message accours the 
right one was used)

/localhome/mare> sudo -k
/localhome/mare> whoami
mare
/localhome/mare> su
Password:
/localhome/mare> whoami
mare
/localhome/mare> sudo su
Password:
off06l01:/localhome/mare # whoami
root
off06l01:/localhome/mare # su mare
/localhome/mare> whoami
mare
/localhome/mare> su
Password:
/localhome/mare> whoami
mare
/localhome/mare> sudo su
off06l01:/localhome/mare # whoami
root
off06l01:/localhome/mare # exit
exit
/localhome/mare> su pili
Password:
su: incorrect password
/localhome/mare> whoami
mare
/localhome/mare> su root
Password:
/localhome/mare> whoami
mare
/localhome/mare> sudo su
off06l01:/localhome/mare # whoami
root
off06l01:/localhome/mare # su pili
off06l01 /localhome/mare> whoami
pili
off06l01 /localhome/mare> su mare
Password:
off06l01 /localhome/mare> whoami
pili
off06l01 /localhome/mare>

Kind regards,
Marcel Reese