[Zope] Problems with animated GIFs

Hi there, I've got a strange problem with animated GIFs: They work fine in any browser. Uploading to Zope, viewing it. Animation goes up to the last frame, but instead of looping indefinitely, it stops at the last frame. Downloading that file from Zope, viewing it in any browser outside Zope, works perfectly! What's going on here??? Any ideas? P.S.: The content_type is image/gif. Do animGifs have another one? Just an idea... Have a nice weekend :-) Lars