I changed my original HDD for a SDD earlier this year and I just got one more SSD for my MBP 13 (2012) that I used to replace DVD drive. I'm using Mountain Lion.
The SSD looks to be recognized allright, but I can't format it.
Then I removed the main drive and tried the new one as the main drive and did the boot using a USB drive with MAC OS and everyhing worked as it should (like I just had one drive). However when I bring the first drive back together with the second they both show up but I can't use it. Seems like I have no permission, but when I look at it's properties it says I can read and write to it.
Thanks a lot!