Audio iChat?

My g/f got her new iBook in yesterday, and she is thrilled with it. I set it up for her at my place, and plugged her into my router so she could get online. Then we felt like trying out the audio chat, b/c we never have before, and it worked pretty well i think. She took her new Mac home, and later that night tried to get me to joinj an audio conference, but neither of us could connect to the other. I've been through the iChat help docs, and none of those helped. Any suggestions to why we suddenly can't audio chat?

You probably need to forward ports on your router

http://docs.info.apple.com/article.html?artnum=93208

I'd try using Skype to be honest. It seems easier to get done...
www.skype.com download the client onto both macs, setup a user name on both, login and you're done.
Skype to Skype calls are free, calls to landlines are not.