boRg, a suggestion that might resolve this!!
In my gallery I upload and image and the exit script generates a thumb and re-saves the image as a thumb as required (in proportion to the origional image or not - as you require).
To do this I've used the image re-sizer dll from
http://www.crazybeavers.se/ (in the products page).... You could resize each time the image is accessed if you want but for performance reasons I prefer the thumb cache option that I use....
Check it out cos it's well cool and is a good work arround for the IE issue (and will also save disk space by reducing the side of the image on the fly)!!! I've example ASP code that I've used for my gallery if you need any but I'm sure you can work it out

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1 question from me (because I've not tried) - will it work with animated .gif's etc - I think so but I don't know perhaps there is more on the site about that....
Also, I saw a post a few days ago that you replied to about converting images to hex for captcha - if I remember correctly this dll can output in an XML format and perhaps that may help (I think the XML output was HEX but you would need to check on that).
Cheers....