It's frustrating but very hard to pin down because it appears to be a quirk in IE not other browsers. The only thing I notice different between a working site and yours is the image links are /SiteImages/image.jpg whereas yours are lower case: /siteimages/image.jpg.
That shouldn't matter because currently the standard is for browsers to be "case neutral" when it comes to urls, but IE is such a flawed browser you never know.
So make sure the images are inserted using the editor - not manually pasted into a page.
One other thing I noticed: on this page http://www.themodelrailwayclub.org/Pages/CopenhagenFields.aspx you are downsizing a large image which caused IE here to freeze up. When you resize in the editor, a browser doesn't know what size to render the image until the page is opening. So it has to first load the full size image and then try to resize it all of which impacts page load times. Fast browsers like Firefox can handle that but it can cause issues in IE.