Um, is there any reason an animated gif or .ani file would not animate in the avatar slot?

They should. Now and then I have a problem with animated GIFs in general, especially with FF, and Viewing Image and refreshing usually fixes it. If it's only happening to you, then try that.

If not, check Control Panel » Images & Icons » Avatars to see if they animate there. Perhaps they weren't uploaded properly, so FTP the images again and see if that fixes it...

If you provide a link I could check them...

Should work fine - we have no issues

Sounds like an issue with the gif as jgeoff says.

OK, it does look like some are working and others are not. I'll import them again and see what happens.

Thanks