I haven’t been able to replicate the bug. I’ve been able to upload a new image from my computer and change my avatar.
In the past, I’ve heard of several strange avatar bugs. All of them were on an individual basis and affected single users. I think we ended up asking Ben to fix it.
I have one idea, which may solve the problem. I could go into the database and remove all of your avatars, so that you can upload from scratch. Hopefully, if the bug is related to the system by which Fluther stores avatars, then this would erase whatever is causing the problem. I don’t know if it will work, but I don’t know of anything else except asking for “professional help.” It’s up to you if you want to try it.