Problem with the MaxScript error
Does the max script have a name like ms3dImportExportVer1_1.ms or ms3dImportExportVer1_2.ms? It might be that the new geometry you made doesn't have group comments, and the script isn't checking for this and the export fails. Try this, select a mesh (group) that isn't new, then right-click to get the quad menu.
From that select properties. This should give you a tabbed dialog. Go to the User Defined tab and see what's there. There should be a group type keyword and a group flag keyword. This is what each mesh (or group if you have Milk shape) should have.
Try selecting your new geometry (mesh) and putting in a group type and group flag entry and see if the export succeeds. Group types should be something like "Body" or "Arms"; the group flag should usually be 0.
The isolated vertex is near the top of the scabbard.
Select and delete it then save the file and try again. One of the two methods should work