This server is using an older protocol than your client.

With the new update as of the 29th, I’ve updated my testing server & tried connecting to my server and its DC’ing me with this error.

Yes I’ve updated the server, did it a few times to verify that it actually worked.
I’ve added -verify all to the startup line.

If any of you ladies or gentlemen have encountered this issue and are able to give a semi intelligent response on how to resolve this issue, please do.

(User was banned for this post ("wrong section" - postal))

Can you post your servers console output and ensure your client is up to date.

Now that you mention it, I look through the server console and see this.

Garry's Mod server.dll Build #131 [Apr 23 2012 15:30:35]

I’ve updated the server multiple times and it says that the server is up to date. Do you know what would be causing this?

That is really odd.

Stupid question but how are you updating it?