iChat Issues

I've been searching for some help with my iChat and I just got off the phone with apple after spending an hour with them.
My iChat won't let me connect to my girlfriends pc so we can use the video conference option. However, we were able to do this last week and had been doing it for quite sometime. I have no idea why it has just stopped. iChat will open the video preview and then a few seconds later it will display "A Communication Error has Occurred". When I click the "Details" option it tells me that that it is "Error:4". I am looking for any suggestions or advice. Apple had me reset my iChat to its original state as well as all of my internet settings. Anything would help!
Thanks.
-Dan