I think I know what is up here, I have this problem on occasion myself. Very powerful hardware and system. All up to date.
Here is what I have concluded.
One, This happens when you're doing a lot of crunching and something is draining the well of resources. I find it might be an unused but still active plug in. Flex editing is definitely a culprit so be sure to turn that off if you're not using it. If there are a lot of 32 bit plugs, that will do it alone. I have found less 32 bit, less trouble all around.
So, It turns out the system is simple taxed for speed and energy a bit more then it can handle. you're going to have to go through the system one thing at a time and try disabling things until it stops. I always do a restart and when it rears its head, I try and take my project, export my files and set them up in another new project to compare what is going on. So far this error has never shut me down, but it can if you keep pushing along.
It really amounts to a lot of load that is starting to catch up to the softwares capability. I suspect it will be resolved in updates. Still working with computers and software in 2011. looking back, it's a dream compared to what I had to deal with just two years ago.
If you wish to upload your project , I am sure we would be willing to run it on our system and see if we too have the same problem. Also, what are all the plugs your using? That is pretty important. Are they 32 bit?