Hello. Thanks for your input.
I got into the habit of always saving my scenes as I work on them. After doing something major in a scene I save it, and always save the final setup before doing a final render so i'm afraid that isn't the solution.
I did find the previous thread here but it seems that no solution was found.   http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2763079

I still can't save.... HELP!!!!
Many thanks