So I set up Yosemite and was installing all the essentials I use. Finally I used Chameleon SSD Optimizer to enable trim, disable sleep image/sudden motion sensor etc. I restarted and got the Circle with slash sign. I tried booting with every different mode I could...pram, smc etc. I had no luck and had to restore from time machine. This has happened back with DP1 and ever since that, I stuck with Mavericks instead. My concern is how do I avoid this? Should I not enable trim at all? I'm using a Samsung 840 Pro 256 GB. (one firmware behind the latest, but that is not the cause of the issue).