I have a Samsung 840 Pro with the same issue. The issue turned out to be the Magician software running in the background. If you keep this from booting at startup your problem may be solved.
Go to the Windows Startup Folder and remove the shortcut for Samsung Magician. It doesn't need to be there; you can just start up the application normally if you need to change a setting.
In Windows 7 and 8, the location of the Startup Folder for an individual user is:
For all users:
If you used the generic "maximum performance" option in Magician, you'll want to go through and fix your power preferences again. It set my minimum CPU state to 100%, not allowing my CPU to clock down at all. Took me forever to figure out that the Magician software made that change.
RAPID mode is a seperate process from magician, and closing one won't affect the other.