Password hashing in MySQL 4.1.0 differs from hashing in 4.1.1 and up. The 4.1.0 differences are:
These differences make authentication in 4.1.0 incompatible with
that of releases that follow it. If you have upgraded to MySQL
4.1.0, it is recommended that you upgrade to a newer version as
soon as possible. After you do, reassign any long passwords in
user table so that they are compatible
with the 41-byte format.