I meant to post this the other day when it happened to me. I clicked on our server and right after the "connection" prompt I get this error message, " client closed down connection check network port 3659udp is open".
Did a Google search and found the following, it worked for me.
open "run"
type "cmd"
type " ipconfig/release"
wait couple seconds
type "ipconfig/renew"
wait for it to complete
type "ipconfig/flushdns"
Good to go.

Interesting... ? I did some port forwarding on the router,
To hopefully help any lag issues.
I get  punk buster"B" error when first get on.
Need to test the services and good to go.
Although,  I had green artifacts and didn't have'm
On other monitor,  remember to check the  connections.