I'm not sure, I cleared my cache and have removed all avatars not showing properly, checked the db and it all seems to tie up now. I have asked my users to re-upload their avatars, fingers crossed. It could have been caused by my edits in the qa-config.php for the image directory. I tried a few things before I could get it to work, initially. I struggled a little setting the correct directory on my sub-domain for the media directory on the main domain.