Yes, this is happening to me all the time. I try to drink some water when the tummy grumbles after eating, because I know I'm not really hungry...if I can stand if for just a short time, it goes away.
I figured it's because I'm used to eating til I'm stuffed, so when I stop at a "normal" serving, I still think I'm hungry, but I'm really not. I also try to eat slower, and eat more fiber.
Maybe when you get the munchies, try a boiled egg sliced up on an Arnold sandwich thin, I find that boiled eggs really keep me full longer than I think they will. Same thing if I eat an apple, it will hold me over.