Hey Gwen,
Welcome to the Club. You are certainly not alone in this though it seems you have been thinking a lot about your thinking. I have been there and can completely relate to what you are going thru. Somedays, it appears that i dont have to do anything, my mind just picks up topics on its own, analyses its, looks at all sides of the situation and tires itself out without geting anywhere - like its on a treadmill. And the worse thing is all this happens during my waking life and without any active effort on my part - its like I have no free will. My theory is that this may be happening bcos. of suppressed thoughts or overwork which causes some sort of chemical imbalance which causes all the pent up emotions to explode. Its like - what I think about a lot during my daytime but am not able to do in real life, I end up doing in my dreams. Its like the mind has a mechanism to fulfill things in the dream world so as to relieve the built up pressure. When this starts happening during waking hours, it is worse bcos. you feel out of control. However, it is just the mind doing its job to relieve itself - in a way, its vomiting all the unpleasant thoughts that have been building up but we have been avoiding and pushing it under the burden of other things (including distractions like movies).
The advisable (and courageous) thing to do is to face the disturbing thoughts head on so that it blows up for sometime and then looses steam. I found that the best ways to do this is to either keep a journal to pour out everything that is going on in the head (which after sometime stops bcos. the cyclical nature gets halted when you commit it to paper where u can see it and acknowledge the problems presence) or to talk it out with an understanding, patient and trusted close person. Both things have the power to help us see things as they are rather than imagining them to be sumthing insurmountable.
I have particularly noted this problem is more with intelligent people having a great analytical mind. The mind can either be a servant or can become the master. Its upto you to let go of the control. The good part about having an intelligent mind is that when you do see things clearly getting out of the problem is much quicker. All the Best and am sure the next time you watch a disney movie, it will not be to escape from disturbing thoughts and trust me, it will be more enjoyable!