I got a 2011 MacBook Pro and had a Samsung 840 Pro installed running Mountain Lion, then Mavericks for about a year without any problems. Without any apparent reason the MBP just wouldn't boot from the SSD anymore, reinserting the old HDD worked instantly. After playing around a bit I made the following observations about the MBP:
- won't boot from the SSD even after cloning the HDD or making a clean reinstall
- not even able to get to the boot menu when the SSD is installed
- can boot from the SSD when it is connected via USB and the HDD is used to get to the boot menu
- cannot boot from any other SSD (tried one from another MBP and also a completely new one)
Any ideas?