I have the same card & mem .After reading posts as far back as 2001, I went back and deleted fog. That was the biggest helper. The only time I get that 'stumble' now is when I have too much on the field and have all controles set up to use. I then delete the things that take up room but you don't really need! Besides, who needs all those people around to watch the ground jump up and get your plane!
GOOD LUCK,
PHIL I.