Flash button inside Movie Clip is not responding to clicks

I am very new to Flash. I've built a Movie Clip, inside this Movie Clip there is a button. There button does not respond to clicks (when I开发者_JS百科 hover over it my cursor remains the same). I know it's not a problem with the button, since when I put the button directly in the main scene it works just great. Any ideas?

Note, I am using flash CS4 with ActionScript 3.

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Ensure that your movieclip's mouseChildren property is set to true.