Is approved not working with Asp net membership with window authentication.

Hi,
I have a system that initially used Forms Authentication to authenticate users. It used the default asp membership and roles provider to handle storing of users details (e.g. username in aspnet_Users table), their status (e.g. IsApproved and IsLockedOut in aspnet_Membership table) and their associated roles (aspnet_UsersInRoles table).
It was changed to use Windows Authentication (e.g. the web.config authentication setting now points to Windows (instead of Forms), usernames in the aspnet_Users table are Windows usernames and IIS Authentication settings were changed (e.g. Forms Authentication disabled / Windows Authentication enabled etc..)). Most things seem to work, in that if a Windows user is listed in the aspnet_Users table then they are logged on automatically. If they are not listed in the aspnet_Users table then the user is denied access. Also users roles are picked up successfully. However one thing fails to work and that' ...