Submission of “Write Post” or “Edit Post” or “Edit Page” etc. semi-fails

Hi there,
I’ve got a problem that is happening most of the time
When I write a post (or page) or edit them – it doesn’t complete the job. Most of the time it gets hangs and times out on “/wp-admin/post.php” or equivalent with the message:

========
The connection was reset
The connection to the server was reset while the page was loading.
* The site could be temporarily unavailable or too busy. Try again in a few
moments.

* If you are unable to load any pages, check your computer’s network
connection.

* If your computer or network is protected by a firewall or proxy, make sure
that Firefox is permitted to access the Web.
========
and the result is either that the post becomes ‘private’ and not shown on the blog, or that it is published but cut off half way through the content.

I thought this was just for really long posts – but I’ve been suffering this now with a post that is only 1.04KB of text.

It happens most, if not all, of the time.

Any clues on how to diagnose?

Cheers

David