If it is happening only with one document, I would try exporting it to IDML and open it again.
Thank you, I have done that already, a bunch of times. What next?
Is it worth trashing InDesign and reinstalling it to see if it is corrupt?
(sorry I don't know how these forums really are supposed to work and the interface is very difficult for me. Been on a MAC since SE30 black and white but since the forums have changes I keep getting lost)