I might have new information for some.
Had to re-bypass the java security again myself, and found out this time I needed my security level on HIGH, not MEDIUM in order to access the chat. This was in addition to adding http//client0.addonchat.com/current/scclient_en.zip to the exception list as instructed above.
Turning it to medium worked for some, but not for me, and it appears to mess up my method and stop it from working, so if you guys tried that method first try undoing it (and I understand some people might be on newer systems than mine and having different problems).