You must have version 9.x of the Machinist Toolbox ActiveX. Note that this must be the *ActiveX* version and not the standalone version of Machinist Toolbox. Is this what you have?
OK, I've got this fixed now. NCPlot was referencing a particular version of Machinist ToolBox. I've fixed it so that it should work with any version of the ActiveX. The bad news is that this fix didn't make into the last update, but will be in the next one.