I have a very similar problem, c.f. PNY CS 1311 SSD doesn't work attached to internal HDD cable. Why?. I've noticed from other fora that this model of MBP has similar problems with certain SSDs, largely as a function of the controller – there are lots of complaints about Seagate Sandforce chips. My problematic PNY CS1311 uses a Phison PS3110-S10-X; your Corsair LS 240Go has a Phison PS3108. Perhaps that's a pattern emerging.