In case you have not stumbled upon this, there is a way to turn heavyweight 24-bit PNG images, into fraction their file size. From the 24-bit, we create the 8-Bit form. We loose the fat, but not the quality.
The 8-bit PNG is an ideal format for Flash. Because they are small in file size, your Flash will be lighter and your website will download faster. Lighter file size also means graphics will move smoother and will be easier on the computer. You will get more wow from Flash.
Besides the size and gain in performance, the core feature of the 8-bit, is its alpha transparency. This is the only format that supports this type of transparency while also keeping a small file size. With this support, you can create visuals that would otherwise not be possible with an opaque image. For example, with the 8-bit version, you can have blurred drop-shadows multiplied over top other graphics.
How to Create the 8-bit PNG
Step 1: In Photoshop, make your alpha transparent 24-bit PNG.
Step 2: Bring your 24-bit into Fireworks, and now in the optimize panel set the optimization to 8-bit, with an alpha transparency.
Step 3: Import into Flash.
Things to Watch
Once you have the 8-bit, you should check its resolution. Depending on the version of the creative suite, and the platform you work on, there may be slight shifts in resolution. Check this in Fireworks, because once saved out as 8-bit, you will NOT be able to open the file in Photoshop.