I got almost all of my forum avatars on server corrupted. They just don't show up and don't download. However, uploads are working normally.

I've noticed some changes in file attributes. Owner is now set to '99' and Group is also '99', but before it was like 'my_login' and 'ftponly' respectively. And I cannot change owner and group myself, because it says, that I have no permissions. I also cannot download these files and delete them.

How these happened, and how can I change attributes back? Btw, is it possible to do that with PHP, I guess PHP have more permissions than FTP-account?