Wireless always validating identity
I'd start by reviewing the event logs on your IAS server for reasoning as to why it's not authenticating your client.
I am using the Windows Wireless Connection Manager. On a couple of occasions I've seen that particular AP (don't know what firmware) suddenly stop attempting to authnenticate clients (it never sends any RADIUS requests) and power-cycling the AP "fixes" the issue.
unless you are running into the initial problem that most older hardware had. You may need to do a firmware upgrade on your device that is connecting to the router. Firstly you can not use WPA, you can use WPA-PSK/WPA2-PSK or WEP.
Secondly you can change the SSID to what you want, and the channel to 1 or 11.
I had already tried the first half of your solution, but I went and did it again just to be sure.
Assuming that you do not have SP3 installed, try to go into your wireless network configuration / configuration screen.(There are several different configurations of wireless, including Zero Config, but we do not know that you are using).
You just have to find the common setting between the two devices.