This is the same problem which I had last winter only I have just upgraded to Starrry night 8 and still I have the problem!!!! Do you remember me Kieren?
I have as before got the PL2303 driver downloaded onto my I Mac. i have aligned the Celestron plc telescope and connect to the i Mac via a usb cable to a usb port, and still I get communication error. I do not know how to configure.