Blender crashes selecting a vert/edge or after a ctrl j


Can anyone suggest why certain .blends i’m creating crash blender on any machine i try it on, both with linux and windows. 2.37, 2.37a and 2.40 alpha all crash.

the blends contain imported 2D CAD drawings. it doesn’t matter whether i import them as DXF or vrml via a conversion program. selecting any of the edges/verts crashes blender or if i try to join stuff together.