There is a major problem with L4D2 servers and passwords.
Firstly, there is no way to password an L4D2 server outside of using the competitive mod, confogl and then setting the confogl_password.
Had you just tried to connect to the server without the password, you would have gotten in(to do so after trying to connect with a password you must type password "" or sv_password "" )
If you're talking about L4D1, which it sounds like you are, then perhaps you misspelt the password when entering it into the GA GameCreate page? Try setting up another with a simple password like 101 or something.
As far as GameArena & their passwords, I can't be sure what else to tell you. Give me some more information, eg which game and I'll be able to offer more help.
Posted on Saturday, 18th December 2010