Images not loading correctly - Grey blocks.

Hi all

I have a demo here to try and illustrate my problem.

It's a simple slideshow photo gallery with thumbnails along the bottom.

The slideshow and the thumbnails are created with the jQuery cycle plugin.

I'm using the NextGen plugin to organise the images into groups.

The images are just added to the page in a long list like so.

      <img class="ngg-singlepic ngg-none" src="" alt="02" />

      <img class="ngg-singlepic ngg-none" src="" alt="03" />

      <img class="ngg-singlepic ngg-none" src="" alt="04" />
so the page is just images.

My problem is sometimes when the page loads the images don't load correctly and the images are partly covered with grey boxes. I have attached images to show the grey boxes because it doesn't happen all the time.

If the images don't load correctly I have to delete the browser cache and try reloading the page, refreshing the page won't load the images correctly.

If the image loads with the grey blocks it also appears with the grey blocks in the wordpress UI as shown in the images attached.

What are these grey boxes, is it Wordpress, the Cycle plugin or NextGen Gallery?

Is it because I am adding the images directly to a page?

Any help with this would be greatly appreciated.