How can a cert authenticate invalidly?

[jjeffery]

Sometimes we see events like this:

This makes zero sense to me since we use certificates installed on the clients to authenticate their connection to the internal WiFi. It also doesn't make sense because the client was happily connected to the same WiFi SSID prior to that and then it connected to that same SSID using a different AP.

For some fuller context, here are some events either side of the one above (not there's one "Beacon Loss", and a couple of "Better AP" events:

The owner of the laptop (my boss!) said that he noticed a couple of times his Wifi icon (in Windows) changed from the bars to the Globe 'disconnected' image, and to reconnect he had to turn WiFi off and back on. That was prior to the screenshots above though.

[Karsten Iwen]

If it is an Intel wireless card, the first step in troubleshooting is to update the drivers to the actual version from the Intel download site.

And for the invalid authentication, the RADIUS log could give you some more information.

[Philip D'Ath]

Check a machine in question - does it have multiple certificates installed? If so, have you configured a certificate selection policy (usually done via group policy)?