I finally cracked this. The problem is with the CPU with multicores. It finally tweaked when I saw the console spewing messages saying things like “thread infinite loop, killed”
The workaround is, when you start the game, press alt-ctrl-del to open the task manager and then select the COD process (CoDSP.exe) and then right click and select “set affinity”. Only select one CPU and then it should be fine.
I haven’t found a way of making this the default, I need to do this every time I start the game.