Can you temporarily enable password retrieval just long enough for the installer to finish setting up your gallery? What is happening is that you specified an account during the GSP install wizard that already exists in your membership system, so GSP is trying to update the password to the value you specified in the wizard. The ASP.NET Membership function for changing the password requires that you pass in the old password, so GSP uses the GetPassword function to get it.
If you don't want to do that, you can rerun the installer and specify a different account that is unique - the code will never invoke the GetPassword function in that scenario. After you are set up you can go into the Site Admin area and make the original account the admin and delete the other one.
(Note: A shortcut to re-running the installer is to use a text editor to update the file _SqlMembership.txt in the App_Data directory to include a new account name.)
Roger Martin
Creator and Lead Developer of Gallery Server Pro