User.Identity.Name is -1

MVC4 application: Does  anyone know what could cause this?  In the Login ActionResult, ThisUserId returns -1 when should return the UserId from the UserProfile table (SimpleMembership).
int ThisUserId = WebSecurity.GetUserId(User.Identity.Name); This started after I accidentally modified the UserProfile table as follows:
public override void Up() { CreateTable( "dbo.UserPresentation", c => new { UserPresentationId = c.Int(nullable: false, identity: true), IsActive = c.Boolean(nullable: false), UserId = c.Int(nullable: false), PresentationId = c.Int(nullable: false), }) .PrimaryKey(t => t.UserPresentationId); AddColumn(&qu ...