Error on page when submitting an image

[onthesce]

Hi all,
I am getting the following error when I try to include an image when submitting news to a page.
Line: 240
Char: 2
Error: 'form_caption' is null an object
Code: 0
url: http://www.onthescene.co.uk/index.ph...nid=1&Itemid=0

Does anyone know how I can amend this. I don't even know where to look for the code as the pages are as you know not static html.
Many thanks
Paul