If a user is already logged in to the site and go in to registeration page and try to register a new user without a matching password, I get a Pop up dialog box that list all the users in the database with a title "Confirm Password Change"

This CreateUserWizard has a Custom Complete Step with couple extra fields.

If I do this from using a registation page with a default Createuserwizard then it does not happen.

Does any one know why or a solution?

Ok here was the cause.
Text field with DateRangeValidator with Type set to Date and Min & Max set to mm/dd/yyyy format dates.

As soon as as I removed this then it started to work like it is supposed to. Clearing ValidationGroup=CreateUSerWizard1 also worked.

Same text field had 2 validators checking the contents one regularexpression to check mm/dd/yyyy and range to check the date range. No I do the data range check in the code.

Is there a solution to this?

The root of this problem is not anything to do with .NET, but with a Feature of FireFox. I racked my brain on this and finally found the answer. I posted details of what exactly causes the popup and how to fix it in another thread

http://forums.asp.net/thread/1383900.aspx