Hi,
This usually points to one of 2 issues:
1. The network traffic is blocked by a firewall (software on the end computer or on the router/modem itself)
2. One or both of the computers have 2 network interfaces (e.g. wired and wireless) and the traffic isn't being routed correctly.
To solve this try:
1. Open Input Director and switch to the "Global Preferences" tab
2. Click the "Change" button under Preferred Network Interface
3. From the pop up window, select the network common to both computers
Do this on both the master computer and slave computer.
Regs,
Shane.