Thanks Paul...it would have been a relief if it were just hidden text, but of course Word tells you immediately the file size & word count so you can confirm immediately that its gone...I've only one clue & that is the issue seems to occur when I'm working in the document and the text jumps into a new page. I can say with some certainty that its when I SAVE from that page, that the text preceding it( on the earlier save pages) vanishes.
I'm finding it hard to fathom as I've had years working with MS Office Word from day 1...and never have I seen this behaviour.