Images not showing in my 2nd Site

This is my main blog, using Wp 3.4.2, all working fine! http://amasociados.es/
The problem is with my 2nd site which is here: http://vivienda.amasociados.es/
When I upload images using the wp uploader they appear in the file “wp-content/blogs.dir/19/files/2012/11” This I think is correct, I can see them via ftp. In the media uploader the url is shown as “http://vivienda.amasociados.es/files/2012/11/3thumb.jpg” however there is a ‘no-image icon’ displayed in the media uploader, also in the library and logically in the post where the image should be.

I have the standard wp .htaccess for multisite with no modifications, in case something is wrong here it is:-

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]

Other settings for the 2nd site are:-

Domain http://vivienda.amasociados.es
Upload path:- wp-content/blogs.dir/19/files
File upload path:- http://vivienda.amasociados.es/files

The url of the image that does not show is
http://vivienda.amasociados.es/files/2012/11/3thumb.jpg
If I put the following url in my browser I can see the image
http://amasociados.es/wp-content/blogs.dir/19/files/2012/11/3thumb.jpg

I am sure I have put a lot of irrelevant information here but if someone can help out with this I’d really appreciate it!