Different Pages Problem

Hi

I have a website at http://www.lothianlife.co.uk which was working fine with permalinks for quite a few months. Then one day last month, without upgrading or changing any settings knowingly, Pages just stopped working. Now if you click on the link to a page, you get a wordpress generated 404 page. Post URLS still work fine, as do archives and categories.

I have tried regenerating permalinks under Options. I have tried deleting my .htaccess file and letting it create a new one. I have tried chmod 644 on my .htaccess so i could manually update the file, but when i clikc the button to regerate permalinks, it just says that it has been updated ok. I have tried adding new pages, but they do not work either. i have tried deleting an old page and creating it again. Nothing works. It is really important to get these working asap, but I am having no luck. i have tried searching the support forums, and have tried all the suggestions i got from similar threads, but nothing has helped.

My .htaccess file looks like this:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

Please can anyone shed any light on this at all? Any help much appreciated.