The MacPlot 1.2 driver that we currently ship under special request is not 32-bit clean. This means that it does not work properly under the memory management scheme known as 32-bit addressing. The DSP (Digital Signal Processor) chips in the new AV computers (660av and 840av) require 32-bit addressing, as well as all Power Macintosh computers, so this option can not be turned off as it could be in older machines.
The Claris version of the MacPlot driver, therefore, will not work on these computers. If you wish to plot from one of these machines, you will need to contact Microspot to obtain an upgrade to a 32-bit clean version of the driver (MacPlot Classic or Pro).
The Tech Info Library article titled "Locating Vendor Information" can help you search for a particular vendor's address and phone number.