Found one FAQ
on Snapz Pro website.
I am having problems recording a game in full screen mode - what can I do?
Last Updated Apr 12, 2007
Snapz Pro X 2 should be able to record most games.
In the Movie settings palette, click on the disclosure triangle, and then check the Smoother (but more CPU-intensive) video capture checkbox. This setting causes Snapz Pro X 2 to directly access VRAM all of the time, which does indeed use up more CPU power, but it will allow it to record movies of games that write directly to the screen.
You normally want this option off, because it affects the performance of the video capture, but for some games, it is the only way to record from some games. Unfortunately, there is not a way for us to auto-detect when it needs to be used, so we had to put it in as a user-settable option.
You would also want to use this option to record things like the various MacOS X window animations to get the smoothest video.
If you are still unable to capture from that game, try playing in Windowed mode. Some games take over the screen completely when played in full screen mode, not allowing Snapz Pro X 2 to even draw the palette let alone capture the video.