IIRC there was a Windows virus that stored data in GIF files
once you got the infected GIF file, the code in the virus was activated to do something.
I don't think that this is the case here, more than likely bad cache memory. Clear the cache, or change the setting to refresh on each page load and then see if the problem goes away.
"Bill Gates cannot guarantee Windows, so how are you going to guarantee my safety?"
-John Crichton to the Emperor of the Scarrans on [link|http://www.farscape.com|FarScape]