Click on the Authentication tab and now uncheck the Enable IEEE 802.1x authentication for this network box.
If the box was checked, then that was why you were getting the “unable to find a certificate to log you on to the network” message because Windows is looking for one, but your wireless router is not setup for certificate security. Once I unchecked that box and tried to reconnect to the wireless network, everything worked fine!
I suspect a firmware upgrade probably fixes that behaviour. If you want to accept both computer credentials and user credentials you'll need to name both "Domain Comptuers" and "Domain Users" in your policy.
By default, XP will re-authenticate with the user credential after the user logs-on (there is no way to do computer-only with XP, I believe).
The client settings on the laptop match the IAS settings and the certificate is definately installed.
In the next window click on the "Authentication" tab, Make sure "Enable IEEE 802.1x...." checkbox is UN-Checked, the rest of this window should be greyed out.
If your network is Encrypted go on to step 6 otherwise Click ok and try to connect to your network again.
Here’s how to connect to your wireless router if you are getting this message.
First, click on the wireless icon in your taskbar and under Related Tasks, choose Change advanced settings.