Hi All, I've just received a brand new 512GB OCZ Vertex 4 SSD to pep up my creaky old Early 2011 MBP, and can't get it to work properly. I took out the 320GB Seagate and put it into an Icybox external USB/FireWire caddy, put the Vertex 4 into the MBP, plugged the caddy into the FireWire socket and switched on. The MBP chimed, so I pressed the 'Option' key to try to boot from my old drive, and ... nothing. Just a grey screen. If I take the Vertex out I can boot OK from the 'FireWired' Seagate drive. Put the Seagate back in the MBP and everything boots as normal (so the cables and SATA hardware is OK). Put the Vertex back in and I'm stuck on the grey screen again. I deduce from this I have a dead SSD to send back to Amazon, unless anyone can suggest something else to try. Thanks for any help. Early 2011 MacBook Pro, 16GB 1333MHz DDR3 RAM, OS X 10.8 (12A269). Trying to replace Apple 320GB Seagate drive with 512GB OCZ Vertex 4 SSD.