This is actually only very rarely an error originated in code, but by your GPU. IDirect3DVertexBuffer9 is a Direct3D interface used to take advantage of dynamic vertex buffers and plays a significant role in optimizing performance during scene rendering. IDirect3DVertexBuffer9::Lock is the function that is called exactly to take advantage of this mechanism and this is usually coded at the core of the graphics engine, not at the game level. On the case of DNF, that's the Unreal Engine.
DNF uses a modified Unreal Engine (and who doesn't these days...). Still, it's very, very, unlikely Gearbox modifications were this deep so they would introduce a bug in the dynamic vertex buffer handling routines. If that was the case this is the type of error you would see a lot of people experiencing, not just you or a small few.
Instead dynamic vertex buffers are very sensitive to your graphics card memory clock speeds (as well as to graphics drivers that ultimately pass on any calls to the GPU). So this is really a problem that will be solved in one of two ways:
- The boring usual "check if you have the latest drivers". However this particularly bit of advice is relevant this time (finally!) because many of the specific game enhancements you usually see in every release can have to do with dynamic vertex buffers.
- If you are overclocking your graphics card, try to tone down a bit the memory clock. It's quite possible that you are overshooting it. If you are, this error is among the first you are going to see.
I'd try the latter option, before considering the drivers option.
Note: If you are confident you aren't exaggerating the memory clock speed, but the problem goes away when you reduce it, leave it reduced and wait for the next drivers release. You may even report that as a bug to your graphics card manufacturer (although chances are they already know).
