Parece que efectivamente es un tema de buffer como comentaba David Pardo.

Image files do not appear when you view a Web page with Internet Explorer 6
SP1
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q817177

> CAUSE
>
Internet Explorer cannot recognize the end of the header area of an image
> file if the end of the header area is at the end of the buffer when the
> image is loading. Therefore, Internet Explorer cannot display the image
> because it cannot recognize when the image has been completely downloaded.
> Note Internet Explorer always uses its internal buffer for loading   data.
> The buffer size depends on the computer environment. Therefore, the buffer
> size dynamically   changes. Users cannot fix the buffer size.


Red X Images missing Fuzzy images Distorted images
http://inetexplorer.mvps.org/answers/51.html
Aquí proponen desde reinstalar el antivirus hasta hacer cambios en el
registro ¡cualquier cosa menos cambiar de navegador! jeje
-- 
_____________________
Fernando Gutiérrez
http://ferguweb.tx.com.ru/
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