I have 3 Macs, iMac, MBP, and Mini. All 3 are set up for network sharing in exactly the same way and functions. Recently the iMac connection fails -- both folder and "shared screen" even though MBP and Mini are listed as "shared" in the finder. MBP and Mini still connect with each other no problem. It's only the iMac that won't connect or allow connections to it. I've rechecked all the sharing settings and firewall, restarted the iMac. None of that works. Any other ideas?