Blank screen after preview or update using child theme

Hi, I created a child theme (parent theme Chateau) by pasting code from the original theme to allow me to change the height of the header image. I’ve also pasted in code for a favicon. Both work perfectly, but now I find that when I try to preview a page, post or other edit – or update it – I get a blank screen, with the following url: http://www.charles-harris.co.uk/wp-admin/post.php

The updates work OK, and there seems to be no other problem. If I go back to the parent theme, the problem disappears. However, when using the child, even if I delete the entire contents of the function.php file between the opening and closing tags, the problem remains…

I’m beyond my very limited expertise and would greatly appreciate some advice.

My site is at http://www.charles-harris.co.uk