Seems like the server won't accept the new file though it doesn't complain. Changed avatar for Christmas and New Years with no problem. The image I tried to change to has worked as a avatar before.
Windows 7 Pro, Waterfox Current (fork of Firefox, up to date)
Ad blocker - off
AVG - temporarily disabeld
Cookies expired
Went to quilt avatar in hopes of resetting something, didn't help
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If I try again tomorrow or the next day it'll probably work. That's happened before.