I was wondering if anyone knows why my permalinks have stopped working.

In the past, permalinks appeared in this form: mysite.com/2011/10/11/title-of-post

Now, clicking on that produces

Not Found
The requested URL /2011/10/11/title-of-post was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

My single post URLs are set as following:

Use extra-path: year, month & dayE-g: http://mysite.com/2006/12/31/post-title

I read elsewhere some advice to change the sample htaccess to .htaccess. I've done that, and I know it's working OK as I am using it to block access to my site while it's in such a mess. (Although removing it doesn't make any difference to the behaviour I describe).

The only thing I can guess is that it's connected with my (unsuccessful) attempts over the last few days to move the site to a new URL.

Is there a way of getting the old behaviour back so that posts can be read in the format mysite.com/2011/10/11/title-of-post ?

Thank you