he remote computer could not be autherticated due to problems with its security certificate. it may be unsafe to proceed.
Windows Vista/2008+ secures the remote connection with a self signed certificate. This certificate only exists on the server and until you import it on your machine, you will get a warning.
How to fix -
You can view the certificate then import it to your local store and it will be trusted.
The reason for this is simply in a large corporate environment, with their own certificate authority, they can give every machine a certificate, and, as the root will be trusted, all computers will "know" each other automatically.