Hmm i'm no pc expert or even close, so i'm not even sure if i follow you guys right.

I can use the same internet connection with 1 ip going from 1 pc to the other pc and join my own games and play with no problem.

I have it setup where my internet connection goes to 1 pc by USB and out by ethernet card to the router to the other pc by a ethernet card.

No idea why it wouldn't work for you...