This error message appears when you first open your project if you have added or removed data from your project directory since you last saved it. To rebuild your project database, select Project |Rebuild from the top of the main WinPICS window.
The map window must be active in order to select this option. The rebuild function finds intersection locations for 2D lines, creates a text file containing line locations and intersections, produces a decimated coordinate file (for quick map displays), and updates the horizon definition table (database). You can select which of these functions are performed each time you rebuild.