CAD tip # 11111:

This is probably caused by using a 3D mouse and hitting its preset 3D view button. This may inadverently rotate the drawing view "in 3D" in the drawing environment and display it flipped. To bring back the normal view, use again the 3D view button on your 3D mouse or run the following iLogic macro to set a standard 2D drawing view:

Dim activeDrawing = ThisApplication.ActiveDocument
Dim firstDocumentView = activeDrawing.Views(1)

Dim camera = firstDocumentView.Camera
Dim tg = ThisApplication.TransientGeometry

camera.Eye = tg.CreatePoint(0, 0, 1)
camera.Target = tg.CreatePoint(0, 0, 0)
camera.UpVector = tg.CreateUnitVector(0, 1, 0)

camera.Apply()