Thanks, @Paul1 .
This seems like it’s probably because you have some other IronPython installed on your machine, such as an IronPython for Revit/Dynamo, that is conflicting with your Rhino IronPython. This issue may be of help in debugging:
In any case, a bug in the IronPython that’s loaded by Rhino/Grasshopper is a bit beyond our expertise to help and you’ll need someone like @wim or @eirannejad to help. Or you could post the issue to the McNeel forum to see if you can get someone there to help.