|Yep, I'm right with you but it seems to be a tricky one.|
I've downloaded the website you gave me and examined its code offline.
The buttons pictures appear to be "png" files.
Can you see about 6 sets of multi-colored circles on that page?
I'm trying to establish whether your computer is able to display png files at all.
One other thing to try. From Firefox go to Tools > Addblock Plus and click Disable everywhere (you can untick this later on). Close Firefox, open it again then see if that helps. I'm trying to find the culprit. If Tools is not showing then hold the Alt key down in Firefox.
Always pop back and let us know the outcome - thanks