Whew. Just about had an emotional meltdown. A couple of weeks ago, I purchased a Samsung 850 EVO SSD for my Mid-2009 Macbook Pro and I went through all the necessary steps to erase, partition, and clone my existing HDD to the new drive using a USB Dock. It went smooth!! Well, today, I decided I wanted to see how well it was performing(start up and using multiple programs at a very fast speed, apparently wasn't enough for me). So, I downloaded BlackMagic Speed Test. Now, I am in NO WAY saying that this program screwed up my new SSD. But, after I installed the program and ran it, checking my read/write speed, I decided to close the program and restart my MBP. That was NOT a good idea to do apparently, because my MBP, would get stuck at start up on the Apple Logo about half way through booting up. Tried restarting in Recovery Mode, etc. WAS NOT WORKING! So, I decided to install my old HDD back into my MBP and start it up. Sure enough, it booted normally. I then plugged my SSD into the USB Docking station and went to Disk Utility. Disk Utility was unable to verify OR repair disk permissions. It also, would not let me erase the SSD and reformat etc. After some successful digging around and using Terminal and Activity Monitor to force quit a task, I was able to erase and partition the SSD all over again. Then cloned it.......again. I then restarted my MBP and held down Option to select the disk I wanted to boot with and success. The SSD is working again, so I installed it into my MBP......again. It seems to be working as it should. I am not sure what ACTUALLY caused the malfunction, as I do not have TRIM enabled(due to Yosemite and I don't want to disable Kext or am I downloading weird software(except for BlackMagic, but it was in the APP Store). But hopefully, it was a fluke. I did, however, go back to Disk Utility after rebooting with the SSD and verify disk permissions and it says all is well. Anywho, this was a scare for me, as I really do not nor can I afford right now, a new MBP... A whole lot of probably, useless info, but someone out there might have had a similar situation. Thanks for being bored to death by that rant!