[When I open my project in plotmaker it asks me to locate ltypeshp.shx
What is this?]
The ltypeshp.shx is most likely a font file from an autocad format. If the drawing was done in Autocad, the font may not be converting properly to Archicad. This may be what plotmaker is recognizing as an error. Not sure if this is the issue that is causing the errors or the crash but you may want to check the text in Archicad and change it to a recognizable font or locate a copy of the .shx file.