Very interesting question and typical of the deep powers of observation we Aspies have...
I know several people with "diagnosed" Bi-Polar Disorders and they all share some of the more common Aspie markers.
1) They are very bright and quickly adapt to new ideas or become bored with the tried and true.
2) They have difficulty interacting with peers except in social/sexual situations where the "rules" of engagement are not yet set by society (e.g. bi-sexual relationships) or are still too foggy to be enforced objectively (e.g. gay marriages). I also know several people with diagnosed Dyslexia (entails much more than reversing letters!) who exhibit severe mood swings similar to those with Bi-Polar disorder.
So what I am thinking is that "Bi-Polar Disorder" may be more of a symptom of other problems that is triggered when someone with undiagnosed Asperger's or Dyslexia encounters the wall of the bubble in which nature has imprisoned them. It is an invisible wall for most but is still a wall of separation between Nero-normal and not so normal.
There's some things you say that sound quite familiar, though I'm not bi-polar. At least, not diagnosed with it.
However; I've noticed that I tend to have moodswings when I'm not doing "my own" things. I prefer things to be new and fresh in some way. I don't care for traditional things a lot. But in that effect I tried a lot of things in my life (and thus gained some skills and knowledge), ranging from playing guitar, keyboards/synthesizers, doing vocals in bands, up to painting miniature figures, 3d modelling, a bit of photography... and the list goes on and on. That also went down with being in college. The courses I took over years had literally no connection (I went from electrical enginering to social work and from journalism to computer science) Besides the normal "aspie" things, I used to have a lot of problems in not being able to keep it new and fresh and it got stale to me really, really fast.
As for point 2... I don't know if it's difficulty, or just me being a bit more "philosophical" about it in the sense that I question those situations a lot. It's not specifically the "this does not work out for me", but also the "why does this not work out for me, and why does it work out for others". But I do have a strong interest in sociology and philosophy.. .and controversy kinda makes me feel happy.
However, I do agree where bi-polar disorder might sometimes not actually be really bi-polar but more that you feel restrained in what you actually want, and more free if you actually have a drive to do what you're up to mentally. At least, that's how it works for me, yet, like I said, I'm not bi-polar. I am however diagnosed with a near perfect score on ADHD tests, so in a way I might have manic episodes, and I'm more likely to have a depressive episode when I'm not using my manic moments for good use on a practical level. With me there's no chemical imbalance in my brain going on so to say, but merely a practical thing... rather OCD-ish to keep busy.