Hi Dimitris,
I've noticed for a while there seems to be a problem when trying to upload your own picture as an avatar, the following error is displayed:
"The attachments upload directory is not writable. Your attachment or avatar cannot be saved."
It works fine if you link to an image on the internet it's just stopping the upload of your own personal image, I've tried it on a few machines just to check that it wasn't a dodgy firewall issue at my end but the problem seems to persist, not sure if you are aware of this, its seems like the directory is either full or read-only.
Regards
Joe