Forgive me if this is not the correct forum...if not, then where?

Dashboard|System & Settings|Update Concrete5
click Check for Update yields error...

5.5.2.1
Warning: Cannot modify header information - headers already sent by (output started at /home/kkmn/public_html/updates/concrete5.5.2.1/concrete/controllers/dashboard/system/backup_restore/update.php:57) in /home/kkmn/public_html/updates/concrete5.5.2.1/concrete/libraries/controller.php on line 356

any help here? I'm new to concrete5 and php.

Thanks.