I'm running WLC 4402, 1242 AP's, ACS 4.x using Windows DB and WinXP SP2 clients.
Clients are authenticating using PEAP MS CHAPv2. I have it set to automatically use windows login name and password.
This works great if the user is a cached user on the laptop but if they have not logged onto the laptop before (eg through wired connection) they are told the domain is not available.
If they go to a wired connection (thus pulling down group policies) and then go to wireless it works fine.
On windows I checked Authenticate as computer when computer information is available ... as seen here ... http://articles.techrepublic.com.com/5100-10878_11-6148574.html ... but it still failed.