This is fixed with Claris MacPlot driver 1.2.
Two issues can occur when using the Claris MacPlot 1.1 driver:
1) Not compatible with the Macintosh IIci, IIfx, or IIsi. If you attempt to use this version with of these, the computer will lock up or return a system error. The new version also corrects issues associated with the Background Printing feature of MultiFinder.
2) Not compatible with Background printing. If Background printing is turned on while the MacPlot driver is selected in the Chooser, the System file will be corrupted and need to be replaced.