Deactivating your devices software. Before you have installed the Port Juggler software you need to temporarilly deactivate any software that could be using your serial ports. Start by deactivating or turning off the software of the devices you will be connecting to the Port Juggler as well as your other serial port. This is to prevent two pieces of software from trying to use the same port at the same time which may cause the Mac to freeze. The most important software to deactivate (if it applies) is the fax software, ARA server, PaperPort software, File Sharing and Graphic Tablet software. Consult your documentation to locate these on/off switches. They are usually located within Control Panels or their own setup software. Here are some examples:     PaperPort's ON and OFF software settings are in the PaperPort Control Panel as well as the port settings.   The GlobalFax software that needs to be made inactive is the "Receive Fax...". It is located in the Global Village Fax Center under the Fax menu.   Wacom and other graphic tablets ON and OFF software settings and the port settings are in the respective Control Panels.