OK, so I have had a Crucial M4 in my MBP (2011) for about 6 months - no issues. Suddenly, the other day - it would not boot. After wiping the SSD and restoring from Time Machine, I can boot to the SSD in a USB enclosure, but not when it is in the Macbook. EDIT - And, the SSD boots fine in another MacBook, so it is clearly the computer. BUT, the regular platter drive works and boots fine. I was on EFI 2.7, but I thought that might be the problem, so I rolled back to 2.2 - no help. EDIT - The SSD is on the latest firmware - 0309. No change. Any ideas?