I'm new here but would it not rewrite 750 at line 484 on cron_daily.php file and check the option "Backup dir. Readable website for FTP users." is checked in "System-> Server Config" "Server tab" the last checkbox.
I thought I had the same problem and I just searched the php code and it seems to me that this is what the true condition.
This option was perhaps not in previous versions.
It is unfortunate that the customer sees the directory if it has no right to read, it is confusing.
I would be fixed tomorrow, but I do not think too much wrong.
Sorry for my English.