CPU Clock speed too low under load.

I went to turn on my PC today and realized that Core Temp was showing me something different than I'd ever seen before. Specifically, that the clock speed of my CPU was maxing out at 3.6 ghz under full load when the BIOS is set for a target of 3.9 ghz with Turbo Boost.

http://valid.canardpc.com/cache/screenshot/2670333.png

Strangely, when the CPU is idle the clock speed bounces around between 3.5 and 3.9... but never reaches those clocks when it's under load. It used to show me 3900 mhz whenever it was under load. Could there be something wrong with the CPU, or something else?

P8Z68-V Gen 3
16 GB DDR 3
Corsair 750W PSU
Gtx 560 ti 448 classy ultra
P8Z68-V Gen 3