That's not normal, especially if it's changing back on you. Can you find the avatars for this user? They'll be in the data/avatars/<s,m,l>/ directories. Divide their user ID by 1000 and round down to find the next directory. The avatar will be <their user ID>.jpg. Are the permissions different in each of the s,m,l directories? How does it compare to the avatar files for your user?
l folder : Same as on my PC. Correct avatar.
m folder: 96 x 96 version. Correct avatar.
s folder: 48 * 48 version. Correct avatar. (which is odd, as this is the version being showed in widgets/online users etc, and is pulling the old avatar.)
I have Gravatar avatar, so I don't pull from my avatar folders, but it works when I test with a local version.
EDIT: Fixed it. Did 777 CHMOD on everything again, then cleared cache and forced purge of CDN cache, and it works now

So probably was just CHMOD/cache problem.