Google sitemaps is reporting an error trying to access the Zenphoto sitemap /cache_html/sitemap/sitemapindex.xml

403 errors are not exactly very helpful, I know. Any ideas? My sitemap is below:

User-agent: *
Sitemap: http://www.landscape-wildlife-photography.co.uk/cache_html/sitemap/sitemapindex.xml
Disallow: /albums/
Disallow: /cache/
Disallow: /themes/
Disallow: /zp-core/
Disallow: /zp-data/
Disallow: /page/search/
Disallow: /uploaded/
Disallow: /backup/

Well, 403 is helpful as it tells us this if you access the file directly:
[i]You don't have permission to access /cache_html/sitemap/sitemapindex.xml on this server.[/i]

Which tells you to check your permissions of the file and folder...;-)

Thanks for your prompt reply! I'm not the most confident at dealing with Linux permissions. I took a look at these and this is how things are set:

\cache_html: 755
\sitemap: 744
Should this be 755?
sitemap-index.xml: 664

Which (if any) should be altered?

It should be 644 files and 755 directories. See also:
http://www.zenphoto.org/news/permissions-for-zenphoto-files-and-folders

Thanks! Permissions changed and I can access the XML file.