Internet connection sharing

I am using Windows 2k on a machine connected to a USB ADSL line and use internet connection sharing to share the connection with a laptop running windows 98 over an ethernet LAN. This works well for normal internet tasks but falls over when, for example I want both machines to join the same on-line game. I guessed that the ADSL connection is using just one IP address which prevents the games from individually identifying the PC’s. Am I on the right lines? And if so, is there a solution?

Cheers!