This problem is addressed in ArcGIS 8.1 Service Pack 1. See Related Information section to download this pack.
ArcMap will not import ArcView 3.x projects that contain empty viewframes. In some instances ArcMap may also crash when you choose such a project in the Import from ArcView 3.2 Project dialog box.
The importer expects the view property of a viewframe to exist and point to a valid view document.
In ArcView 3.2, either delete the empty viewframe or change it so it references a view in that project.