This is my second Bytestor 4GB, urgently replacing my previous one, out of manufacturers warranty (just) which suddenly died on me with no warning. One moment I could copy my files, and then suddenly the device shows as 'full' (it wasn't) but with no readable files on it, nothing in the content, and no way to open, explore, recopy files. Just death.
Researching some of the other flash drives, it seems as if this is a not unfamiliar problem, even with the more expensive sticks. So.......replaced with a new Bytestor, this time in a pretty girlie pink Fortunately the vendor delivered the new one incredibly quickly and I didn't have any hard drive death, so my precious files are safe. But it does mean I won't ONLY rely on this as a backup, and will make sure to do a second back up periodically. One Bytestor flash drive the 'belt' - need a second as 'braces' too for really secure backup of precious files.