iChat hates me

iChat isn't really the main culprit here Roy, it's more the routers that sit in between any two people on the internet that are causing the issues. I'll try to simplify this into a non-technical metaphor that will probably just end up confusing you even more, but why the hell not.

Think of your router as an apartment building in the big, complex, neighborhood of the internet. When you try to send something to a well known place (google.com for example), your computer can figure out the "mailing address" (ip address and port) to send something to because they have an exact address for their "building" (server). If you send something to an apartment building's address, who knows where it's actually intended to go, since an apartment building can have tens of hundreds of tenants behind that one address (just like you can have multiple computers behind one router at home). When you try to communicate with other folks in these "apartment buildings" you may end up sending something to the front office instead of a specific tenant.

Continuing with this metaphor, iChat tries to figure out it's own "box number" so it can tell whoever you're trying to communicate with your exact "mailing address" else you might get "return to sender" errors when iChat can't figure out exactly where to send data.

Basically, iChat is trying to do the best it can to figure out the exact mailing address of both your computer, and the individual with whom you're trying to video chat with, but it can't for some reason, thus the communications error.

(Extremely simplified, but I figure this shuold help you at least understand it to some extent)