There is some decent animation, and some of the scenes look kinda cool, but it isn't all done particularly well; in several places the tweens didn't fit together properly, or just looked cheap, and in some places teh graphics didnt fit together either- there were gaps on and around the stage that shouldn't have been there. Make sure all background graphics overlap teh stage at least slightly, otherwise you get gaps around the edges in Flash Player, which I think can really spoil the easthetics of a flash.
Also, you should have used some alpha gradients on the sun to make a corona effect- if you did do any of the graphics in photoshop it was unnecissary- you can do all that stuff in Flash. Try playing with the colour mixer.
I don't know why all your other movies would be too big- overuse of bitmaps? unoptimised sound? you can compress both on the publish settings in Flash... but try to minimise the amount of bitmaps you use. Bitmaps are good if masked onto stuff as textures, but they shouldn't be used as main graphics excessively.
Keep practicing, your future looks bright!