Select Mac but Nothing Changes
You can see your Mac listed after clicking the Air Display icon on your computer, but nothing changes on the Mac screen after being selected.
1. Go to the Air Display system tray icon and choose About...
2. In the window that comes up double-click the computer monitor in the image (not the iPad screen) and then click OK to close the window.
3. Exit Air Display on your PC and relaunch it.
4. Try to connect again
If you get an error message regarding your IP address, then the will be to change the DNS servers on your PC (in both your wired and wireless configurations if necessary) to Google's Public DNS servers. Here's a link with instructions on how to do this, http://code.google.com/speed/public-dns/docs/using.html
1. On your primary Mac go to System Preferences>Air Display and select your secondary Mac again from there.
2. If you get an error message regarding the firewall, go to System Preferences>Security on both Macs and try disabling the Mac firewall