Seems like it hasn't finished exporting.
I had to force shut my computer.. re saved my document, and still gives me the same message when I am trying to export...Not a big fan of InDesign.. I guess I will just go the old slow way, Photoshop>Acrobat...
Force quit can cause all sorts of strange problems. Make sure there is no trace of the PDF, export the ID file to .idml, open that and save as a new .indd and try again.