In testing, the user on a db i\'ve used was a big jefe. In production, he only has Execute.
When I called,
Membership.DeleteUser(user)
Maybe better to make sure the user that executes the delete membership has the to correct ASP.NET Membership sql roles. In my case I was deleting a membershipuser that has some roles and profile properties. The delete method failed, but after assigning the correct sql roles it worked.
ALTER ROLE [aspnet_Profile_FullAccess] ADD MEMBER []
ALTER ROLE [aspnet_Roles_FullAccess] ADD MEMBER []
You could also add [aspnet_Personalization_FullAccess] if you are using that functionality.