This means that the backup account has run out of its allocated quota. Please contact TruskaBackup Support to increase your backup quota.
You can contact us by:
Web : From this support portal, just raise a ticket - http://support.truska.com/support/tickets/new
Phone: 028 9751 9550
There will be a cost associated with increasing your quota.
The alternative is to review what you are backing up and maybe reduce the amount in another area or remove some sections of your backup.
You can archive older files that are unlikely to change to a DVD and then remove from the backup set.