bizarre image issue

hi people, posting this query here as i'm not quite sure where it fits..

I have a win2000 server box running ibm apache 2.0.42 and IE5.0 (don't blame me for this set up!). there's a real issue with some gifs being displayed - it will take 4 or 5 refreshes before some are shown.

however, this only happens with gifs produced in MM fireworks 4/MX - images saved as jpgs from fireworks, or gifs/jpgs from other graphics packages are fine.

this is really annoying me! I know it's just a matter of using a different package to produce the images, but MM products are of choice in my company. are there any issues around IE5.0 and rendering heavily compressed gifs? i'm pretty sure of the server set up, so i don't think it will be that. i know IE5.0 is a pretty crap browser anyway... or do later versions of fireworks use more modern compression techniques??

any help would be greatly appreciated... not much fun spending weekends in work sorting issues like this.