User password problem on a password policy applied box

[a bv]

Hi,
On a Redhat 4x or 5x box which password policy applied  a user with
sudo permissions cant login cause of the  password not accepted. The
root pasword is  not reachable and the box is a production machine
which is serving services and cant be rebooted easily. Cause the
password policy makes the user change its policy, the user thinks if
he have fogotten or not the recent password. But trying the similar
passwords didnt worked, and he thinks if his user account is locked
for a long time. So how can this issue can be fixed?

Regards