I just got my new 2012 Mac mini today and I'm having issues booting off an external USB3 SSD. My plan is to simply replace the 1 TB HDD that shipped stock with a Crucial M4 512GB SSD. No second drives, no additional internal SATA cables, nothing. Just an in-place swap. Knowing that these 2012 minis shipped with a special build of OS X, I decided to install OS X onto my SSD externally and confirm normal operation before I opened the mini and took everything apart. I first attempted to use the Internet Recovery from the 1 TB stock drive (and special build of ML) to install the special build onto the external. It found the drive, downloaded the OS, and installed it. When it was time to reboot, the system would show the "no" or "do not do this" or "do not smoke" sign and hung there. When I rebooted back to the 1 TB drive, I checked the external SSD and saw that it did in fact install the OS (free space was lessened). Then I tried something else: I used Carbon Copy Cloner to clone the 1 TB drive and its special OS build onto the external SSD. Again: everything cloned just fine and when I rebooted the system, used the option key to pick the external SSD, it went to the "no" or "do not do this" sign and hung. What is going on here? I even went out of my way to update the firmware on my Crucial M4. It's got the latest firmware. And before I did any of this, I used the same external USB-SATA adapter and connected the drive to a MacBook Air, booted 10.8.2 off of it, and made sure everything was functioning. It was perfect. This SSD and adapter are normal. Do I have to teardown the mini and put the SSD into the SATA slot to get it to work? Is it more troublesome to boot off the external than just the primary SATA slot? What's going on here??