In an 80 page doc, the pasteboard has come over the page, but only on about a third of the pages?! So, where it has, it affects the zooming shortcuts, i.e. zoom to pasteboard has no effect, because the whole area is one big pasteboard!
Pasteboard problems are usually cured by a trip through .idml See Remove minor corruption by exporting
If that doesn't solve it we're going to need some screen shots, and the version of ID and your OS.
It worked! Well, the pages have come back but the images are all a bit strange in their boxes. I can live with that. A quick run through on the affected pages and we are back in business!
Many thanks Peter, if for nothing more than the sheer speed of your reply!