Constant freeze and crash when moving in 3D viewport

I'm using fusion in production having not touched it for a few months and I'm getting constant freezes when manipulating simple objects and particles in the 3D viewports. I'm having a hard time narrowing it down but one pretty consistent way of making fusion freeze seems to be to open a new comp, load Rony's "burning engine" preset from the recent (great) particle examples he posted here, then pull the render node into the right viewer and the merge3d node into the left. If I start moving things around (seems to be particularly rotation but that could be me) in the 3D viewport very soon fusion freezes, I get the spinning blue circle (I'm on win7) and it doesn't come back, just sits there frozen.

I'm getting this as some point on pretty much every medium to complex 3D scene I try and work with. My immediate feeling is graphics driver issues - I've tried it on Fu6.4, the last Fu7.01 eyeon release and the current Black Magic with same problem, and I've updated the drivers a couple of time in the last few months, so I'm going to downgrade to some older ones to see what happens. Just wondered if anyone out there had any thoughts before I start reinstalling? Many thanks in advance.

I'm running win7, 64bit, 32gig mem, nvidia quadro k3100m driver 347.52.

Rotation often results in resorting of transparent meshes. Can you try with different transparency sorting modes?

Does it happen with preview controls disabled (ctrl+k)?

And you mentioned that it's happening when you view both a 3D viewer and a 2D viewer after the 3Rn. Can you get it to crash using just 3Rn's or just 3D Viewers?

Thanks Chad. Tried it with just 3D viewports open and it didn't seem to crash. Then tried again with one 3D and one render (openGL) viewport and got a freeze within a couple of minutes. Changed the sort mode to accurate and tried again, freeze. Changed to software renderer, although it froze for ten seconds or so at one point it recovered (there are a fair number of particles, but not insane). Put it back to OpenGL renderer and bizarrely had a frozen rendered image that didn't change when I moved the light in the viewport, but changed lighting when I moved the 3D object! It was as if moving the 3D object in the 3D viewport was actually moving the light position in the renderer. Weirded me right out. It then froze again.

I did try running with control K selected in the 3D viewport - I don't really know what this does, but all the wireframe and display objects (manipulators, camera field of view etc) disappeared. I moved the camera viewport around a bit and it didn't crash, but without seeing the manipulators I couldn't really do much else.

Anyone using quadros running the latest driver on the nvidia website 353.30? Thought I'd try this as a starting point . . .

I've attached the simple comp file I'm using to test this. A fair few particles but previously this machine handled much more complex scenes with many more particles and no freezes . . .

Thanks Chad. Tried it with just 3D viewports open and it didn't seem to crash. Then tried again with one 3D and one render (openGL) viewport and got a freeze within a couple of minutes. Changed the sort mode to accurate and tried again, freeze. Changed to software renderer, although it froze for ten seconds or so at one point it recovered (there are a fair number of particles, but not insane). Put it back to OpenGL renderer and bizarrely had a frozen rendered image that didn't change when I moved the light in the viewport, but changed lighting when I moved the 3D object! It was as if moving the 3D object in the 3D viewport was actually moving the light position in the renderer. Weirded me right out. It then froze again.

Ok, good clue. Were you rendering any other channels other than RGBA? Did you have supersampling on? Fusion is neat (or not neat, depending on where you stand on this feature) in that it gives you WYSIWYG shaders in the viewports. They're the exact same Cg code for viewports and the OpenGL renderer. They don't even recompile, the compiled shader is cached. But if you have other channels in the 3Rn, those have to be generated, assigned, and rendered without alerting the user. There might be something in that loop.

I don't really know what this does, but all the wireframe and display objects (manipulators, camera field of view etc) disappeared.

That's what it does. You can still use hotkeys or use the tool controls to manipulate things. I just wanted to know if drawing those was causing an issue. I've only seen it a few times where it did, but it's an easy thing to rule out.

I've attached the simple comp file I'm using to test this.

I'm not seeing it.