Occlusion culling doesn't works.

Hi everyone. i'm making a game, but it has a big object. So that helps the game goes slow. But now i want to using the occlusion culling to make it faster, because everything behind the camera will remove untill the camera is shyning to the points. But when i'm using the occlusion culling it gives me a direct error. I enabled the Static of that object. and now to bake the occlusion culling. it gives this error with a new window send/ don't send.

The error is Error occurred in PVS computation. This is probably due to running out of memory or a problem with the graphics card. Try decreasing the near plane or defining smaller PVS Volumes. Don't lock the computer during PVS computation.

But now, i have a new computer with the newest intel core i7 with a great grapghic card specially for games. i'm using microsoft windows... AND UNITY 3.3 PRO

someone can help me?

you need the pro version for occlusion culling support as far as I know, do you have that?