Weird Prompt on Windows 7

So I get this weird prompt on Windows 7 every time I try to access a network resource. It's a prompt titled "Enter Network Password" and the error at the bottom says: "The system detected a possible attempt to compromise security. Please ensure that you can contact the server that authenticated you."

This error (and the long delay accessing the network resource) remind me of a similar issue in the past (like with Windows XP) but I'm still searching my memory banks...