If you go to the page that shows all of the available image formats, the original file still works:
http://www.instructables.com/file/FWDSO7QHAWBX38T/?size=RECTANGLE1

I've had problems using animated GIFs before on Instructables. When uploaded the Robot resizes it a bunch of times for use around the site. Thankfully it keeps the same image format (GIF) but I found it doesn't deal with the layers very well. I managed to get it to work by uploading the animated image at the right size, IE for the one above, large, which is 768x1024. Try resizing your gif to that size then reuploading it. It's an annoying workaround I know, but I can't imagine fixing GIF support is a priority for the developers.

An alternative is to just use the static (non-flashing) image in the picture, but add the original GIF using HTML in the actual Instructable step. You'll need a Pro code to do that, if you want one, I have some spare, PM me and I'll give you one. Or PM me if that makes no sense and I'll try explain it better.