I am able to export all of a small site without problem and the site concerned here in the past.
A moderately large site fails probably because the WordPress servers will take a long time creating the file, a guess based on what I can test, an hour. In consequence the probably very simple export script leaves the browser to timeout. Keeping retrying (same request) has not worked.
I've tried different browsers, same result. (but IE6 doesn't work at all)
An export of a small part of the site succeeds.
Is the only solution pay WordPress $129 each time?
Seems to me the file ought to be in archive form anyway.
It's not clear from the text of the export page whether "all" can be time staged. From function it appears not.
The blog I need help with is tallbloke.wordpress.com.