By terminating the core of GameGuard you also terminate it's capability to answer with a valid answer to the ClientServerAuth (CSA) packet sent from the server. Without an answer or with a invalid answer the server will disconnect you after some delay.
To prevent it you can emulate the packet function with a custom application by peeking the connection pipes. Though, judging by your summary I don't think you got the skill to do that. No offense intended.