Same solution as I found for my nw-a1200. The diagram is misleading. That vertical crossbar will remain in situ, it's attached to the main unit. The circular disc around the crossbar is the bit that comes off. I levered it and it started to come up on one side, I got under that with some tweezers and away it came. You can then slide the back down and off. There is indeed a diagram on page 83 of this manual. ftp://ftp.vaio-link.com/pub/manuals/consumer/2659086111.PDF
Good luck.
Ray Godwin, November 2008