I've had trouble getting animated GIFs to transform properly on my Craft site.
I've installed Imagick on my server, and set $imageDriver to imagick explicitly. This seems to have allowed some GIFs to transform but not others. I've tried GIFs I've made myself in Photoshop, and GIFs found online, with completely mixed results. No rhyme or reason to it at all as far as I can tell.
A GIF that resized correctly: http://craft.kingzog.com/img/_thumbnail/OH-TEE.gif
And one that didn't: http://craft.kingzog.com/img/_thumbnail/tennis_gif.gif
(I'm not allowed to post too many links, but of course you can remove /_thumbnail from the URLs to view the original, still-animated GIFs).
I'm stumped. Anyone have any knowledge about file formatting, config or anything else that might help?