Basemap layers are not supported in versions prior to ArcGIS 9.3.1. If you create a 9.3.1. package basemap layers will be converted to a group layer. Basemap layers will remain a basemap layer when the package is opened in ArcGIS 10 or later.
Solutions
- Be aware that the basemap layer will be converted to a group layer.
- Alternatively, remove the basemap layer from the map.
More information
The basemap layer conversion to a group layer will preserve the appearance of the map when opened in ArcGIS 9.3.1, but it will not maintain the high-performance interaction that basemap layers have in ArcGIS 10 or later.