I'm getting the same thing, and I have the 8400GT. But sometimes it's fine? Maybe it is lag? Generally for me it happens when i'm on the ground, but certain systems (Such as Reglus) seem to have the effect as well.
The game tells me I need to update drivers, but every time I download the Nvidia update it tells me my card is not recognised!!
I was having the stutter issue.
I run a nVidia card.
There is a new driver. it was released after the date stamp on your post.
Also, go update your sound drivers.
For me the issue of ground / starbase stutter was fixed with 2 new drivers