As requested I am starting a new thread so you can troubleshoot more easily?
Here is the text of my post again:
"all the menu items appear as top level despite having set all pages to correct levels and resetting the appearance/menus function.
When I save the menu all items revert to top level."
I am using Twenty-ten theme.
Problem first occurred on 1 Jan 2013.
The site is http://tideswelltales.wordpress.com/
The blog I need help with is tideswelltales.wordpress.com.