Efficient Frame-by-Frame Animation with PNGs?

Does anyone have any recommendations for efficient handling of frame-by-frame bitmap animations?

I’m putting together an app with an animated character that stands on screen and moves around doing animations. Each animation (Talking, Dancing, Jumping, etc) is an individual Movie Clip made up of around 50+ PNGs in sequence. I’m using CS3 to create the clips, and export them as SWCs for use in Flex.

The problem is memory usage. It seems that Flash will place the entire movieclip into memory , and when we are talking 50 frames, 256w x 256h, 24-bit color, 8-bit alpha, that’s a lot of memory (so (256*256)*4 = 250k each frame * 50 frames = ~13 megs of memory for each clip). Couple that with the fact that Garbage Collection doesn’t seem to happen very often, and this simple little app takes can take up 300megs+ of memory.

I’ve never put together an app with this many PNGs (2000+), so any advice is appreciated.