@psychobunny no, I have not, but I suspect it may be plugin related or something screwy about this thread in the database. I have been distracted by a million other things and one misbehaving thread wasn't my priority, but I will look and see if I can figure something else out.
Users will still be able to upload their own avatars though. There isn't a setting to disable that, but for the time being you can set "Maximum User Image File Size" to 0. Created an issue for that specifically: