The Error 39 is very common with the Prolific serial equipment. This mainly occurs as the driver had not been installed correctly. Prolific makes good equipment however for some odd reason the serial adapter has a tendency to show a driver error. This error tends to occur with the PL2303 serial adapter.
The first step if it is an error 39 is to uninstall the driver in your Control Panel and re-install the driver again. This fixes the problem.