...but successfully change when they are displayed in posters messages.

The same is relative to users signatures. I can delete the signature endlessly but it still appears intact.

I must state that previously I used the LoudMouth (which is now dead for a year already) forum that also used ***_users table of Joomla! db for some users details.

Avatars previously uploaded through LoudMouth are shown if they are mooved to avatars folder of the FB but it is impossible to delete them after that. I mean I can delete the file but FB continues to try to show the deleted picture. FB deletes files well but does not change anC related MySQL fields at all.

So it seems to me that FB uses one MySQL field to display and recognize the avatar in the Profile window and the profilebox at the top and another MySQL field for displaying avatars in messages.

And as FB can't recognize the avatar presence through profile editing form it always deletes avatar when profile is changed.

Please excuse my bad English.

I'm not sure to have understood everything in you message but an issue about avatars that was deleted while editing had been submitted by f4nag.
The problem seems to come from an "include_once" used instead of a single "include" in admin.fireboard.html.php apparently line 2654 (FB 1.0.1 beta).

Could you try and confirm ?