Unplayable framerate and unusual CPU usage

Hello there,
I've recently been having some issues with the game's framerate.
Up until the past few days it's been fine, but since then it hasn't got past 5fps on any map (including Grid, Small, Pure and Gridmap) with all mods disabled.
With physics paused it's perfectly fine and acts just as it did before, at over 70fps, however this cannot be said for realtime.
In realtime, the engine sounds' audio pops all over the place and the camera has massive amounts of stutter to go with the framerate.
What's also odd is that in the menus, it reaches over 70fps according to MSi Afterburner and is as quick and responsive as ever. It's only when a map is loaded in with a car that the framerate drastically drops.
Also, when in a map in realtime, only the first two cores of my 6-core AMD FX-6300 max out at 100%, and every other piece of hardware - including GPU memory and physical memory, as well as all the other cores - is at barely over 10% usage.
BeamNG is not using inbuilt graphics since this CPU does not have an integrated GPU; it is using my 2GB MSi GTX 770.
Keep in mind that all mods are disabled, and it is kept at Normal settings with AA, SSAO, Light Rays, Dynamic Reflection and DOF all off. Lowering this to even the lowest preset has absolutely no effect whatsoever.
I have re-installed the game, cleared the cache and verified the game's integrity with no issues found.
Any help would be much appreciated.

For whatever reason, the forum won't let me post images, and I think it's because (as others have found in the past) my account is labelled as 'new'.

 

That sounds like exactly the same issue I had after a graphics driver update got released. I had to install a the new version of the drivers and it worked perfectly.

 

I'll try that and see if it helps.

It began to happen when I was editing a version of the 200BX, which had been moved into a separate archive and renamed as a different car. After experimenting with JBeams and having a few Lua errors, this lag began, but usually went away either after a game restart or a reboot of windows.
This separate mod that I had running worked fine up until these errors, (which I found in the Lua console), and the errors were simply syntax errors, occuring when the game tried loading in a configuration of the car. It aborted loading once it found these errors and left the map empty with no vehicles, however when a different car was spawned (not being part of this mod) this lag was present.
No software or driver updates have occured between boots of BeamNG recently.
--- Post updated ---
This issue has been successfully fixed by a driver update! Thanks guys. This thread can now be locked/deleted.

 

That did fix it for a time, but after starting the game today the same issue came up again. And when my driver breaks, as you can imagine, it doesn't just slow down BeamNG.
I re-installed my driver twice this afternoon, and everything else on my PC ran smoothly - but when I booted BeamNG, and it lagged again, everything slowed down with it.
So I've come to the conclusion that somehow, BeamNG.drive is doing damage to my Nvidia graphics driver.

 

I do have images of that, but as I say in my first post, it wouldn't allow me to post images before.

 

This is accurate according to all programs I've used. At full load, it gets to around 21°C, as I've got quite an adequate heatsink and cooling system.
The game ran fine at over 80fps yesterday, after the driver update completed, and this processor was bought new. So I don't think it's the processor's fault.

 

While paused I get a solid 75fps:
Unusually, as said, the first two cores hit 100% usage while the others aren't so much. When the game is running correctly, I usually tend to see all cores running at around 70% usage, but rarely 100%.

The power plan remains on High Performance with no power saving options in use.
No significant software or driver updates (apart from those to do with the GPU) have occured recently, at least throughout this issue being present (as far as I recall).
It is definitely odd that updating the video driver temporarily fixed the issue. I'm quite confused at this, since I've updated again since, and it has not fixed it. I will try again to see if it fixes it once more.