Thanks BD Aqua. Your suggestions guided me to a solution:
• First tried all 3 suggestions. None worked, but they started me thinking:
• Disconnected the Firewire cable, restarted Laptop 2, reconnected Firewire. Now logged in on Laptop 2 as Roger.
• Logged back in as Wife (the normal situation). Now iMac can see volumes on Laptop 2, after a short delay bar "authenticating Roger…". However, Laptop 2 can't connect to iMac! (There may have been another couple of steps that I have forgotten)
• Turned off Internet Sharing on the iMac. This improved things some more.
• Finally, what I suspect was the decisive step: In the iMac Network Port configuration list, moved "Internal Modem" from last to first, followed by Firewire. (This is as per kb article HT 2246 - iMac shares its dial up connection with both laptops.) Everything is rosy (and I have learned some more about the whole Apple Accounts/File sharing/Permissions set up!) Now I have complete 3-way file sharing and simultaneous Internet Sharing, the ideal situation. Hallelujah!
Postscript: The kb article referred to above is titled "Internet Connection & File Sharing" This is accurate, but that article does not really address "Internet Sharing & File Sharing", which requires, additionally, that the Gateway machine be nominated by the others as a router.
Many thanks for your inspirations!
