Connecting iMac to MacBook Pro via Firewire problem

Apple's instructions for connecting desktop computer to laptop, both running Snow Leopard, starts with:

"Connect the two with a firewire cable, go to System Preferences > Network and highlight "firewire" in the left pane. The little light next to it should change to green. Do this for both Macs."

my computers are connected with a firewire cable (cable works - i checked w/ an external hard drive).

in the system prefs on either/both computers, the button does not change from orange to green.

another user had this problem and posted about it Feb 2012, a year ago, and never received a response.