It's likely a permissions issue on either the /home/mysite/public_html/ or /home/mysite/public_html/images/avatar/ directories.
Can you check to make sure those directories are writeable by Joomla?
If things seem right, can you check if the /home/mysite/public_html/tmp/scprofile_315_pic_tmp.jpg file exists on your server and is a real avatar picture? If so, that means the likely permission problem is on the /images/avatar directory.
Let us know how that goes, and we'll help how we can,
Alex
Avatar move image error
