That is soo odd. We have the same setup except for Video card and over clocking. Have you tried deleting the contents in the "USER" folder then launching again?
Haven't tried that yet, but will right now. Is your CPU overclocked? Mine is in the bios, but I am going to reset the clock to see if that makes a difference.
EDIT: Also, the gameplay is silky smooth in the arena commander mode, and none of the graphics settings affect the frame rate while online, so I really do not think it is an issue on my end. But I am about to update my drives with a clean install and delete the user file, and default the CPU clock to see if that makes a difference. I really just want to land on a damn planet already!