MBP with Mountain Lion 10.8.3 loses connection to system SSD at random times and freezes
A firmware update for that SSD was released early this year: have you updated?  The release notes mention:


  Resolved a power-up timing issue that could result in a drive hang, resulting in an inability to communicate with the host computer. The hang condition would typically occur during power-up or resume from Sleep or Hibernate. Most often, a new power cycle will clear the condition and allow normal operations to continue.


(Personally I'm using a CT128M4SSD2 and have decided not to update unless I encounter issues.)