Hi, there are many false memory stick clones.

Here (http://www.sony.net/Products/mssupport/datarescue/en_2/form.html) there is a form where you can insert model and serial number of your memory stick directly from Sony site.

I think this is a useful news, for who buy with internet.

Here some more background info:

CLICK (http://forums.vr-zone.com/showthread.php?t=59400)

The pictures on that forum are not working anymore, but there is some good info.