Replacing configurations with encrypted passwords

I recently had to apply a saved configuration to a 4500 series switch
after replacing the supervisory engine (II+). I've done this kind of
thing in the past without any problem, but this time I had some
problems with the passwords. For example, there was local usernames
like:

username user password 7 <hex string>

But I was unable to log in until I changed the password in the
configuration I was using with a plaintext version and reapplied it to
the switch.

Has the level 7 password encryption algorithm changed?

Thanks!
.