Okay, here's what you do. Crop the .gif down to the MAXIMUM AVATAR SIZE using a cropping tool Go to your file that has it Blam You have a .gif avatar.
For the gif to animate for Avatar images, it must be smaller than 230x230 pixels. If you need help send me the image.
I've had that problem before. It's why I didn't have a gif avatar until somewhat recently. You have to make sure that the gif is less than 230x230 pixels AND 683.6KB in size. I know that it says "or" on the settings page but it seems like my avatar had to fit both of the criteria. Hope I helped.
Vbulletin automatically converts avatars don't meet the above criteria^ During said conversion it does not preserve .gif animations so you need to ensure that you're .gif avatars do not need resizing (they are beneath both the dimension and file size limits).