It might be worth working out HOW they're getting that message. Is the error on the support website or yours? Is it trying to upload an image, or use a link? Check to make sure they're using the image button and not the video button. Also check to see if they're inserting using the quick reply or proper reply box. And that's assuming that when you say "to the website" you mean to the forums ... or is it the image gallery, wiki or somewhere else?
How weird (and Hi "Frothy" lol ... not sure how we should respond to that name!) .. the only time I've noticed the problem was on the support forums, and it was never really a problem, I just thought it was me doing something wrong. Don't recall seeing it on my website.
Glad it's getting worked on tho ;-)