The differences between Netscape and IE are quite frustrating! HTML is a standard but each implements the standard in a different way.
But, as it has been said, "The great thing about standards is that there are so many from which to choose"
To answer your question;
One technique that works well is to pre-cache the images. You can do this by placing HTML code such as I have below right after the closing BODY tag (but before the closing HTML tag).
This loads each image into the browser cache but does not display them for the user. However, by being in the cache the browser can retrieve them instantly without going to the server.
I would advice that you modify your site slightly to provide an INTRODUCTORY page with this 'hidden' codeon it. As the user reads your introduction the images will be cached in the background. Then when they are needed to be displayed there is no delay (with Netscape or IE) and no funky flashing.
---------------------------