I too am loving this book; you have such a fine way of explaining the material, not to mention all of the files help!
The Section about changing password / Chapter 9
No matter how many times I try, the password doesn't update, the only message received is "Error! The email address and password do not match those on file."
I registered myself and viewed the new record when the View Users page loads.
Another troubleshoot, I copied and pasted the password from the record in phpMyAdmin.
I would send you my code, but it is the same code from your download area.