We've got CTI plug-in integrated into our FileMaker system.

When it gets a call from someone, it kicks filemaker script, passes caller's ID and shows Customer's Info. It's working perfectly.

The problem that we are facing now is that Filemker gets disconnected from the host sometimes.

Then it shows this error "Communication with the host was interrupted and could not be re-established. All affected windows will be closed."

Once this happens, it never work untill I restart FileMakerPro itself.

I tried to figure out to overwhelm this but in consequence had no idea:(

You cannot command or kick any script while FileMaker pro is showing error message.

This system is running on MacOS Lion.

Is there any good way to detect disconnection error and restart FileMakerPro?

Try running a network cable between the robot (client) computer and the switch nearest the server, and/or replacing all cables/switches in that path. Despite all the advice against it, I have never experienced problems running a robot on a server computer. You cannot trap this error within Filemaker. Obviously, addressing the root cause is preferred. Absent that, you can use Applescript to detect the error dialog, send a key to acknowledge it, and re-open the file and run a script, similar to what 'Okey Dokey Pro' used to do in the OS9 era, at least the acknowledge part. So you would activate the application & send a keystroke. I haven't used Applescripts for a couple years, presumably first, you'd test if client was disconnected, I'm assuming Filemaker fails to respond to Apple Events in that case and could be detected that way, otherwise you'd have to search for the window. Alternately, you could just use two files: an opener and the remote client DB. Sending enter acknowledges the dialog; you then delay, and send the key to run macro #1 of the opener, which opens the remote DB and starts the script. Or the Applescript could directly open the remote file & run the macro.