Ask the user to shut down any modem extensions or communications control panels.
Any powerbook (or desktop for that matter) that uses an internal modem will almost always have some control panel item which tells the computer to active the internal modem. When this is done, the internal modem's software activates itself on start-up and begins polling the modem port for serial data transmissions. When ANY X-Rite device attempts to communicate with ANY software over the port, the modem software grabs the data and feeds it to the modem. This effectively prevents any communication between the software and our instrument. The user will always have to disable the internal modem to continue.
On the PB180 for example: go into the PowerBook "SetUp" control panel and switch it from internal modem to external modem.
On the PB520C the same control panel must be switched from Compatible modem to Normal modem.
For PowerBooks with an internal modem and the Express Modem control panel: the Express Modem, "General Settings" screen has a checkbox in the lower-left, "Use internal modem instead of Modem port". This checkbox must NOT be checked!. Otherwise the instrument communications are directed to the modem.
There are a vast assortment of programs designed to utilize the modem and or printer ports on the Macintosh platform. The Applications Support staff at X-Rite receive many calls from frustrated customers. Most of these calls resolve themselves as being in the realm of those items listed above. In brief, please check your extensions and control panel items before giving up hope. This is not so much a software issue as a limit of the Macintosh hardware design.