I have tryed Posting with Norton Personal Firewall 2003 and Zone Alarm PRo 3. When I was on norton Personal firewall, I couldnt post, it would take me to a page and say "Cannot Post, Invalid Host"

But it works with Zonealarm Pro 3.5 IF I dont have it set to block 3rd party cookies? Does mirc send 3rd party cookies?

The forum relies on cookies, yes. Most forums (the truly interactive ones) rely on them. They only perform basic tasks like storing your login details so you don't have to type your password every time you come back.

One thing to remember, don't use two firewalls on the one machine. They'll usually conflict in some way and is therefore a bad practice.

I dont use them at the same time. I used one, reformated, and used the other. But, I have my firewall to only block 3rd party cookies... so why is it blockign mirc? it shoudl accept the cookie.