Uploads for subdomains

Hi

On one of my subdomains I uploaded a header image as part of the theme.

The image is actually saved at
mysite/wp-content/blogs.dir/2/files/2011/09/final_02_norm_size2.png

and I can see it if I enter the above url in a browser.

However, it is not displayed on the blog where the url there is apearing as:

https://uk.mysite.com/files/2011/09/final_02_norm_size2.png

It is as if the latter url isn’t being correctly converted to the former.

Has anyone got any suggestions please?

Thanks
Mark

PS – My .htaccess file is as follows:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule . index.php [L]

# END WordPress