GIF images not displaying in Chrome/FF but are in IE

I have been given a set of GIF images to put on a site as downloadable banners. The GIFs were made in Photoshop CS4 and saved for web. Also tried saving in CS6.

In a simple bare .html file the GIFs display in all browsers
On my local Apache server, and remote, in Firefox the GIFs are grayed out (no display) in Firebug and a mysterious class gets added (with or without JS enabled) class="ohpzmoxfjlujhttypwqv"
On Chrome the images are also not displayed. Chrome adds the following to the GIFs: style="display: none !important; visibility: hidden !important; opacity: 0 !important; background-position: 0px 0px;" width="0" height="0"
With or without specifying dimensions as attributes or in the style.
The GIF I tested with different Save-For-Web modes in PS was a simple two frame GIF with a 4second pause on each
I have tried manually specifying MIME type in Apache, it isn't a MIME issue.
3/4 of the GIFs I tried from the internet worked. One had the same issue.
All the GIFs work in IE

Anyone experienced this witchcraft before and knows what is going on?

Thanks

Here is one that doesn't work (but does on this site!). Making me think it is some strange Apache config. enter image description here

Solution

Its AdBlock plus or another adblocker...

Deactivate it temporarily and retry...