So pretty much this dialogue is asking you if you are OK with sending your credentials to this authentication server. You will always get this the first time you connect to an 802.1X network (wired or wireless) unless the client is preconfigured with something like ClearPass QuickConnect or via group policy for AD-joined devices.
In Windows 8, they made the text of the box a little more clear for the end user (less like an error):
The idea is that once the user trusts the specific cert chain and server name, they will be prompted with the same dialog again if they connect to a network with the same name, but different AAA infrastructure on the back end. Someone can easily stand up a network with the same SSID and capture the users credentials in the EAP transaction. That is why its so critical to ALWAYS check the server certificate and server name. Only turn it off on the client for troubleshooting.