That topic, while it may well be the problem, does not seem to contain a solution (ie I have no idea how to do stuff like that).
It contained a link to a site with basically all the info there is on it, but to cut out some of the hops:
1) Go to
http://portforward.com/english/routers/port_forwarding/routerindex.htm (if it pops up an ad for PFConfig just X out of that)
2) Click the name of your router brand (or select it from their dropdown list)
3) Click the name of your router model (or select it from their dropdown list)
4) On the next page, click "Default Guide" in the third paragraph of normal-size text.
5) It will give you a series of instructions and screenshots from your router's interface on how to do the port-forwarding.
That said, if Himachi works (and is fast enough), then none of that's necessary. Once on Himachi just use AIW's Direct Connect (or Direct IP, I forget the button name) function and enter whatever their IP is within that Himachi network (won't be the same as their public IP).
