Preview post not working

[Heathercowper]

I'm having a problem with the Preview Post function - can anyone help?

http://www.heatheronhertravels.com/

When I press the Preview Post button I am getting the error message "Sorry, no posts matched your criteria"

Previously this was working perfectly and has only been a problem in the last few days.

The only changes I made recently were
1. Added a new page and sub-page Work with me/Guest Posts
2. Changes some code in the Feedburner plugin to set up a feed based on categories

I've tested changing both these things back to the way they were but it does not correct the problem. Any idea what else may be causing this?

Many Thanks
Heather