Dani,
Very sorry for the delayed response.
Nothing on your site should ever be 777, because that means anyone can right to it. The proper way to set the ownerships is to let as few users have access to write, and never let 'anyone', which is the last 7 means.
In general, if you're using Linux and have the ability to chmod (change permissions) and chown (change the user that owns the files/directories), you should:
* Go to Help->System Information
* Click "PHP Information"
* Search for "User/Group" in the Apache section (can be named many different things)
** You should see something like: apache(12)/12
** This is the user and group that Apache and PHP are executing under.
* You should then chown your files so that they are owned by either the user or the group as set shown above. That way, instead of assigning "everyone" permission, you can use a permission like 775, which is writeable, readable, and executable by the owner and group.. but everyone only has read and execute permissions.
Whew. Hope that explains a little bit behind it. With that all said, and if it's a permissions issue, it's likely the import of the user's avatar. I don't remember where offhand that goes to in Kunena (can look it up if you'd like), but I'd recommend checking that folder and any subfolders there.. or simply disabiling the Avatar import functionality. The field import shouldn't be a problem, and disabling the "Always Import" will turn of field importing as well as avatars.
Good luck,
Alex