ERROR
This problem is addressed in ArcGIS 8.1 Service Pack 1. See the Related Information section to download this pack.If a shapefile is used as a mask for an analysis operation, an error, "The cell size value is either invalid or not defined", is returned when using the Raster Calculator.
This is a known issue with ArcGIS 8.1.
Article ID:000004085
Get help from ArcGIS experts
Download the Esri Support App