I just got an iMac. For the first few hours it was turned on, my MBP showed up in the iMac's Finder, and vice versa. However now, for the past two days, neither Mac has shown up in the others Finder. Connecting to afp://[their ip address] lets me see the public folders, but I still can't use the shared iTunes libraries, or share screens. The same thing happened with the MBP and other Windows/Linux devices on the network, as well as my jailbroken iPod with Netatalk installed, but I just chalked that up to the klugey nature of mixed networking. Guess that wasn't the problem. Does anyone have any ideas on how to fix this?