I've had my 520 since August and one thing that always bothered me was sometimes when I would reboot or reset the drive would be missing from the BIOS as my boot drive. If I power off and back on it would work as normal I would just need to setup in Bios again and list it as the primary HD Boot device.
This happened on the following motherboards and so I'm sure it's not the motherboard:
Asus Sabertooth P67
Asus Sabertooth X79
and now I have the Asus Rampage IV motherboard.
The other think I just noticed is my CorsairLink software shows 0 for Drive Temp. I also installed HD Temperature and while the software reports the health is OK, it says Temperature: Unsupported. Also my SSD Toolbox can access, optimize and interact with the device fine. Any ideas?
Trying using a different SATA cable for the SSD. I really like the blue SATA cables that ship with the newer intel motherboards. They click and lock into place real nice and support the SATA 6 speed. The older red cables are very hit or miss.
As for the temperature thing, the unsupported message may in fact be what's going on. There is no SMART field for temperature as reported in the toolbox. Don't worry about it.