COD Black Ops 2 Problem

I have an m14xr2 with 8gb of ram, gpu 650m, i7 ecc ecc
In the last two days I had some weird issues with call of duty black ops 2 multiplayer
I have everything setted on max specs, I have an average of 75-85 frames/s still the games doesn't work properly... seems like it lags during the gameplay
I tried with battlefield 3 and other games and everything seemed as perfect as always
the weird thing is that the "lag" (it isn't proper lag, its just that the game dowsn't run as smooth as it did yesterday) happens only during that specific game and not while playing other games
What could have happened?

Please Help
Thanks for your time

PS: I didn't install new drivers
do you have your nvidia & intel settings, your command console settings, and your COD BO2 settings all checked? im running at 90+ fps, when i noticed lag in gameplay i realized my power cord was unplugged and i had different performance settings for that.

also check your device manager, make sure your nvidia card is actually working, i got my m14xr2 from ebay, it came with a burnt card caused by bios update A09, i got a new motherboard and card through warranty and since i have stayed at bios A07. scared to upgrade lol. but yea if your graphics card is good then your drivers for the device will check out

my dedicated intel hd 3000 was able to play most games untill the nvidia was replaced