If this video is so important to you. Then you should image the flash drive while in mass storage mode so that the data is safely backed up before any further damage is done to the missing part of the clip. I'm not sure what image program will work with flash drives. I've tried WinHex hex editor to make a binary file of the flash drive. It works but a sector by sector copy is very slow. Since the n900's flash drive is fat32. Cloning the drive to another drive would allow you to dig deep into the file system to see where the damage was done and possibly find that missing part of the clip. Fixing a broken file is easy if the file isn't fragmented and hasn't been overwritten.