Just had to share this fix I found, it has got the game running the best I've had it so far.
"I've been subjected to a full dose of problems with Black Ops - out of the box it was unplayable, extreme stuttering and frame rates jumping from 60 to 15 crazily.
Patch did't really help.
Shadows off/vsync on helped smooth things out a bit but still the suttering continued.
Then i tried this (found it on the steam forums)
Go into your cfg. file (for both multi and singleplayer) and open it in note pad
press ctrl + F and search for "seta r_rendererPreference" without the quotation marks
It should say "Default"
Change it to "Shader Model 3.0"
Save.
Fixed all of the stuttering for me. Frame rate still isn't where it should be but it usually stays above 45 and never goes below 30. I know it seems like an illogical fix, but it honestly really helped me.
Give it a try.
My specs:
e7200 @ 3.16ghz
4 gigs ddr2 ram
ATI HD 5850
Windows 7 64 bit"
Source.