There is a solution outside of SQLServer if the normal database backup method fails. Is there a backup performed of the actual files on the server - e.g C:\ drive contents etc using e.g. Veritas or similar? Or check if there are any Shadow copies of the C:\ drive (right click on C:\ drive, properties, Shadow Copies. If so you can recover to the time of the last back up of the files. If Shadow Copy is not enabled - then enable it for the future - it is a life saver.