Disappearing images!

I have been scouring the net for 3 weeks looking for an answer to this.

I recently moved from a single wp install to multisite. As a result, all my images show initially, but as soon as the page finishes loading, they all disappear – except one or two.
THIS ONLY HAPPENS IN GOOGLE CHROME (OSX)

• The theme I am using has support for multisite.
• If i open the image in a new tab it is there
• The ‘missing image’ displays the right dimensions, but just a broken image picture
• the theme uses timThumb
• i have emptied the cache, and it aggrevates the issue – i.e., sometimes, the images won’t disappear (im assuming they are being cached by the browser). As soon as you empty the cache though, more disappear (but not all images!).
• Ive used other peoples computers, same issue
• the issue occurs both front end and back end – see this screencast => https://www.screencast.com/t/cUYKSegW0N
• it only occurs on the subdirectory sites, not the ‘root’ / main / base site
• URL is 2ndcity.co.nz/users, or /parents

could this be an issue to do with the lack of a “www” in the title?

Heres my .htaccess

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

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?blogN/files/(.+) wp-content/blogs.dir/N/files/$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]