Branches of node trees randomly disabling themselves

Anyone see anything like this before?

I grade my sequence, add color fx, everything looks good, I add to render queue. While rendering, I notice that random clips (1 out of every 5, maybe) aren't displaying properly. I cancel the render, go back into the color fx room, random groups of nodes are disabled though all of the nodes are set up correctly (no pass-through, etc...).

So to fix it I select the nodes, cut them, paste them back in, and voila! everything looks normal again.

Then I start to render again and another random batch of 20% gets messed up. Since I'm only re-rendering the changed clips, I'm slowly making progress, but this is bizarre.