Sorry, it is a Crucial M4 256GB in a late 2011 MacBook Pro. This could be the known problem where the drive stops working after 5000 or so hours of use, which is resolved by an update to latest firmware. Unfortunately, it will not mount/be detected at all, either in the HD enclosure in the computer or in an external USB case. I have tried Disk Utility and TechTool Pro with no luck, and am running 10.6.8.
Crucial have offered a replacement, but if I can fix it somehow I figure it would save me some time.