Smartphones asking for certificate when connecting to wireless

[nLinked]

We are using a RADIUS server (Network Policy Server) installed on Windows Server 2008 to authenticate AD username and passwords when connecting to wireless. Laptops connect just fine without asking for any certificate. iPhone's ask to accept a certificate. We're not using any certificate as far as I know. Is there a way so iPhone's will just connect without prompting this? I want it so the username and password are accepted and that's it.

[Geoff]

This is an iOS5 bug afaik.

[DavidYoung]

Its probably because your certificate on the NAP/IAS server is either self-signed or created by a self-signed CA and the iPhone doesn't trust it, so it has to ask the user. Basically, if you want this to go away, you need to get a commercial SSL certificate to install on the server.