Problems with low frames per second are usually related to memory or graphics.
I would recommend testing the following components:
Physical memory: Try testing different memory sticks or one memory at a time.
Graphics card: for driver updates please check http://www.geforce.com/drivers
I would also recommend contact the board maker for additional information.
As I said, Allan, the problem is not the GPU. The GPU runs just fine at 60%, 70% while de CPU is in 100%. The exact same moments that theses frame drops occurs are the moments that the cpu hits its maximum usage. So, no, the problem is not related with my graphic card.
Thanks for the reply, though.