I flew IFR 350nm + This afternoon using the default ATC and got on to approach and it crashed, so unless FSUIPC affects that as well it seems the fault is not with PF3 as we've been thinking .
I've tried to download and install Air Traffic Manager which in FSX days was a really useful tool to reduce traffic.
However, I've never managed to get it to work since I went to P3D although it says it is P3D ready.
So what I've done is as I usually have Air Traffic in the sim' limited to 50 on the bar, I've now reduced it to 40 ie by 20%.
We'll see if that works, although these aren't OOM's, they are plain and simple computer crashes.
This is all so frustrating that its almost time for me to seek out a new hobby where everything works without all these complications.

John