What CPU are you running?
What motherobard are you using?
What BIOS version?
From my experience with using AOD on some AM3 and FM1 chips, it's not accurate. It takes the temperature reading...below the socket or something.
Use CPU-Z, HWMonitor, or AIDA64 to monitor your CPU frequency and temperature.
You can also try using your motherboard manufacturer's software (if they have any).
Erm...do you have any power saving features on? Cool N' Quiet? etc? These fill reduce the clock frequency when the system is idle to save power.
Phenom II X6 1090T @ 4.1GHz // ASUS Crosshair V Formula 990FX // Sapphire Radeon HD Dual-X 7970 // Thermaltake Frio w/ push-pull (using Antec Formula 7 Nano Diamond paste!!) // 8GB (2 X 4GB) G.Skill RipJaws DDR3 1600MHz @ 8-9-8-34-21-1T // Corsair TX850 850W // Corsair Force GT 120GB SSD (OS) // Kingston 200 V+ 120GB SSD // WD Caviar Black 1TB // Windows 7 Ult x64 // Logitech X-540