Just my opinion, but I think your old core 2 duo is simply not up to the task of 64 bit OS and Pro Tools. Maybe you forgot that you can up the buffer to lessen strain on the computer?(go as high as available). Also, watch the cpu meter and see what it does when you add certain plugins(like the J37 you mentioned). I was on quad-core machines back when PT10 hit and moved to 6-core by the time 11 was released. Each new version requires more horsepower to run the added features
