cant connect to other computers on my network

I have three macs on my network. my gf's ibook, my powermac, and my powerbook. I can connect to my G5 from my powerbook, and to my g5 from the ibook, but not vice versa. I can see the ibook and powerbook under network, but when i try to connect it times out.. ive tried restarting. what can the problem be?

Make sure personal filesharing is turned on on all three computers, they are all on the same subnet and have similar IP addresses (look under network in system prefs). I think you also need to be using DHCP over ethernet (no manual settings).