i also have both FB3 and flash builder in my machine.. after seeing your post, i tried with the same situation, but cant produce the error.
- required flash player ( in project settings ): 9.--- in FB3 / 10 in FB 4
- both run fine without FP version error.
Install the flash player 10 debugging version it work good for flash builder 4
and in flex builder 3 set the following properties of project -> Flex compiler -> set the Required flash player Version in HTML wrapper section to 10
this will works fine
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Haha, you should have made that line flashy-red and bold!!