Not running MovieClip timeline code

Hello.

I have a movieclip, and for some reason, the timeline code isn’t running.

Stage, frame 1


var my_mc:MovieClip = new MyMC();
my_mc.name = "my_mc";

MyMC is a properly linked Movieclip.

MyMC, frame 1


stop();

trace("Hey look guys! I'm alive!")

That trace statement doesn’t happen.
Also, when I put a breakpoint on the “stop()” I get an error saying:

Breakpoint not set; No executable code at line 1 of Symbol ‘my_mc’, Layer ‘as’, Frame 1

Any ideas, anyone?