Nested buttons on a MovieClip problem

Hi everyone,

i have this problem

i have a movie clip and inside that MC i have a menu with some buttons(they are also MovieClips), my buttons(MC) inside the menu MC are animated by the mx.transitions tweens, all of that works fine.

then i want to put my menu with some transparency by default and restablish the _alpha to 100% when i rollOver the menu, when i do that the change with the _alpha propertie works fine but my buttons inside the MovieClip no longer works, can someone explain me why???

i attach an example of the problem, to see the problem just uncomment the last lines of code.