I haven’t seen the little red X for years - back in the days of slow connections, it was quit common if a timeout prevented the image from being downloaded, but heck.
One thing it could be is a cache problem on a proxy server at your ISP - some ISPs still set you up to access the internet through their proxy servers (not sure why - maybe they skim the data to target you with ads or something).
Have a look in your internet connection settings - in IE6, it’s Tools>Internet Options>Connections - then Settings (if you’re on dialup, or something that resembles it), or LAN Settings (if you have an ethernet connection to a router)
If the ‘use a proxy server’ option is checked, try unchecking it and see if that helps. Make a note of the proxy server address settings before you do this, in case they disappear after unchecking.