I'm not sure if this is only my problem or everyone else have the same problem as me.
I tried uploading a custom avatar, every time I try to save it, I was prompted "Unable to save image". This happens for both methods of linking the image from PhotoBucket or uploading from computer.
However, the "do not use avatar" and using pre-defined avatars are functioning correctly.
I am sure that my image type and image size (120x120 px and under 30 kB) are appropriate for the forum.
This never happened to me and this is also the first time I tried updating my avatar after the forum upgrade.