Bake lightmaps on terrain, not enough RAM

Hi, I am in desperate need of someone who could take a look at my lightmap settings. Somehow, it says that I run out of Ram after exporting to beast. I am using Unity Pro 4.3.

My specs are:

-Ram: 16GB

-CPU: i7-2600 with 3,40GHz

-GPU: NVIDIA GeForce GTX 560 Ti

thanks in advance