Marco,
We heard about this issue in mid-February originally with the release of JomSocial 2.8.3. Our understanding and all tests indicate that the issue was on JomSocial's side with the very first release of 2.8.3 they put out. They later updated the release (without changing the version number) and we haven't had any other users commenting on the avatar upload issue since.
The original thread about this problem can be found here (the link is to the post with the resolution of the updated 2.8.3 version):
www.sourcecoast.com/forums/jfbconnect/jf...connect-error#p30961
If your directories are writeable, there should be no reason within JFBConnect that we can't copy it. There would appear to be a problem within JomSocial at that point. Just so I understand your upgrade process.. you were on 2.8.2, you went to 2.8.4 and then you downgraded to 2.8.3?
Can you try downgrading back to 2.8.2 to verify that it works again? I don't have any other great ideas, unfortunately.
Thanks,
Alex