If you are using color, or 16 or more shades of black and white, there may not be sufficient memory to run Claris CAD effectively.
Select Control Panel from the Apple Menu. Select "monitors" a dialog box will appear allowing you to reset your colors. Select black and white and the number 2, so that you are working with two shades, black and white, only. This change will take effect immediately, there is no need to restart the machine or Claris CAD.
Color documents require substantially more RAM memory than do black and white documents.