On Saturday morning we discovered our server had suffered a fatal crash overnight. The primary hard-drive had died.
Thankfully, we had a backup from Friday evening, so it only affected a few hours of orders. All customers whose orders were placed between the backup and the crash were notified and these orders were re-created in the system from the email confirmations.
No orders were lost and, despite our web site being down for most of Saturday whilst the server was rebuilt with a new hard-drive and the backups restored, there was no other problems and everything is now back and working fine.