To me it sounds like your game gets stuck when it loads stuff.
Is your hard disk almost full or slow for another reason?
I think hard disks get slower when they have a lot of small files on them or are full over 90%, or maybe its super-fragmented.
Your gigahearts seem a bit slow, but I dont think its the reason.
Dual core processors still help, because although FL will use only one, the other stuff running on your computer (for example video recording software) will use the other one to spare the one running FL.
The thing that increases my FPS the most is lowering the resolution, but your stuck problem sounds more like your hard disk is slow. Maybe also your virtual ram setting isnt optimal for FL.