Need Some Help

My friend is working on a game (part of it is coded by someone else which left the project).
This is the problem the passwords are in sha1 and once the person logins in it changes to somethign different and hes trying to make a login script.
Ex.

Upon Registration its:

After first login its:

 

You need to post the login page so we can see what it is doing.

 

Probably wrong mysql queries, cause password changes, password cant change by it self , it need to update by script, so correct mistakes in update queries!