There is a firmware issue on the Crucial M4 drives that can manifest itself during an abnormal shutdown. When attempting to boot the drive (or access it if it is NOT the boot drive) the bios will tell you during boot that the drive is not accessible. The solution is to to a “Power Cycle” on the SSD. The instructions to do so are found here: http://forum.crucial.com/t5/Solid-State-Drives-SSD-Knowledge/Why-did-my-SSD-quot-disappear-quot-from-my-system/ta-p/65215
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The procedure is to apply power only to the drive for 20 minutes, remove power for 30 seconds, apply power again for 20 minutes, then the drive magically heals itself.
The real solution is to apply firmware version 040H or later.