That AES 256-bit encryption doesn't work properly on Kingston's SSDNow V+200 and KC100 solid-state drives, so the company had to go on record about the matter.
The two storage devices don't actually perform anything above 128-bit encryption, despite what the spec sheet says.
It's not Kingston's fault though. The shortcoming is inherent in all SSDs equipped with SandForce controllers.
LSI, the one who has recently bought SandForce, found the problem just days ago and is working hard on a firmware fix
In the meantime, Kingston has promised that the people who actually use 256-bit encryption will be allowed to swap their drives for fault-less ones when they become available. Fortunately, the number of buyers who consider the encryption critical is fairly low, so the problem hasn't caused any big crises.