While detailing and sectioning views after zooming extents the drawing plan view has disappeared (Single layout). It is not hidden, isolated or anything else that is possible, just invisible. When searching the drawing views on the design tree the plan flashes in an orange colour, the dimensions and section marks remain in place but the solid and hidden lines are not visible. Have saved and closed and then re-opened the drawing but still no plan view. Shut down SW and the PC and after re-opening there are lines of a sectional view created from the plan view now missing as well, but still dimensions remain. Is this a common fault with SW because other colleges are saying they have similar problems also. Re-drawing and detailing again is very time consuming on large drawings.