Your internal hdd has a faulty, please contact your local distributor for a service. Full lists can be found here, http://www.nextodi.com/store/nvs_offline_store.html
Answer by Chris2013-05-15
Ask your country distributor to upgrade your NVS2501 to SSD internal storage. SSD is 100% safe from physical shocks, knocks or shaking gestures. It sounds expensive at first sight, but you will love it once you feel how NVS2501 operates with SSD installed. Good luck!