I am running Leopard on a MacBook Pro 17" and shared networking is always grayed out. I have tried Parallels versions 5160, 5570, 5580, and 5582. I have tried uninstalling, rebooting, manually removing files, using the uninstaller, reinstalling, and have searched the forums for other ideas but I am coming up empty. My bottom line is pvsnatd is running but the NAT ports never appear in the Network system pane (only the original AirPort, Ethernet, FireWire, and Bluetooth) and therefore the option is always grayed out in Parallels. I have uninstalled, reinstalled, and rebooted so many times I am about to give up and simply migrate to VMWare. I know that works on my machine and I would like to compare both side to side but thus far this issue has been a deal breaker. If anyone has any hints as to how to get the Parallels NAT ports up and running please let me know.