export doesn’t include all posts?

I’m trying to export m wordpress content using the built in export feature which creates a WordPress eXtended RSS file.

The process seems to work for the most part but for some reason it leaves out content created since march 7th 2008.

I’ve taken a look at the content on march 7th and I can’t see anything odd or special about it, any ideas? as to what could be causing content from march 7th onwards from being excluded?

Thanks for any advice you can give.