Recording several games, and not others

Hello,

I'm using CamStudio to record different computer games I ran over an not-so-terrific system.
It works fine with GTA IV and Need For Speed:Shifts, but for an unknown reason (to me (-:),
I cannot record Call Of Duty:Black-Ops 2. The recording comes out as a black screen on which you can only see the cursor moving.
I tried it on a different computer (better configuration) - same results.
Also tried in "Windowed" mode, which didn't help (I'm not sure he actually ran it on a window mode... maybe it's impossible to run such a game in that mode, or maybe I did something wrong, or maybe the Steam platform interferes).

I would really appreciate any guidance, after failing in finding relevant data on the support forum (the questions always depict this problem as occurring in all the recordings, and in my case - it's only one game).

I should probably mention I'm running on Windows 7.

Thanks!