I have multiple stores and websites it seems the ability to change the web site is no longer available somehow. What would cause this option to be grayed out?
Goto to table "store_group" from phpmyadmin or any mysql client you are using.
Edit that table now udpate the website_id manually after that open the admin and edit that store you can now see website has been changed save the store again. This will gray down the website dropdown again.
Hope this helps!