Left 4 Dead (1) - Disconnected after 10 retries

[Pixelated_SMILE]

So basically yesterday I bought 'Left 4 Dead' and it was working perfectally. But for some reason today every time i try to join a online server no matter the game type it always comes up with the message "Disconnected after 10 retries". Iv tired changing the client port, uninstalling and then re-installing the same message keeps coming up. Has anyone got any other solutions that i could try, its really bugging me and want to get it fixed.
Thanks!

Update: Found out it was Firewall/virus protection, as firewall does not allow connections to come in it will disconnect you! Just turn off Firewall

[Ŧђɇ ƼϮϞ §μȑ√iⱴ۞ѓ]

Never disable firewall. You're asking for trouble by doing that. Your firewall setting has nothing to do with the "Disconnected after 10 retries" message. That message means the ip you tried connecting to is offline or doesn't allow external connections to it.

If a friend of yours has a local server, they need to forwards the ports L4D uses on their router to allow incoming connections to the server. But never disabled the firewall.