There is not a method to delete only the drawing. There are two approaches to solving this.
One, you can delete the floor. On the main page, click on the Facilities menu on the left. Then click on the Floors menu. This will launch a dialog to browse the floor records. Find the floor with the bad drawing and delete that floor record. It will take the drawing with it.
Second approach, import a new drawing to the same floor. It will overwrite the prior drawing for that floor.
If you still have drawing lock-ups with DWF files that open in the plain DWF Viewer, log a support case for some one-on-one debugging.
Mark Evans
Autodesk
Mark Evans
Senior Product Manager
AEC Division, Simulation Product Line
Autodesk, Inc.