ArcView returns this error when opening a project that had a shapefile auto-labeled when opened the last time:
"Illegal Operation in module MSVCRT20.DLL"
The shapefile that you auto-label was generated by converting an ArcInfo coverage to a shapefile. The coverage may have contained sliver polygons.
Build and clean the Polygon coverage to get rid of the sliver polygons. Then, convert the coverage to a shapefile and auto-label.