Black Ops 2 FPS Drops?

[Ibreakthings]

When i play zombie maps ill have 120+ FPS and it will drop to 20 or so then shoot back up for a couple minutes or so. Its not when i aim in because i still get 120+ FPS. I had to turn my graphics settings all the way on low because i was playing at higher settings getting soild 60 FPS but it dropped to the 10's so i had to turn it down. What is the reason behind such things?

Overclocked Components:
Q6600 3.2GHz
GT320 (+68 Core +175 Mem)
1280 x 1024 @ 75Hz
G.Skill 2133MHz 10-11-11-31 Running at 1333MHz 6-7-7-18

 

[Ibreakthings]

Its only in Buried and Orgins all my other games never suffer from FPS drops

 

[Thomas Lee]

please let me know when you get results. this is happening to me too FFS.. I'll be perfectly fine at 180 FPs on BF4 and boom it drops to like 11-20 fps for like a couple seconds. half the time, this is how I get killed... it happens so randomly too....