removeChild on an MC from my library

Hi,

I have an MC that is called from my library when there is a specific error in my movie. My problem is that I cant manage to remove the movie clip when it is on the screen.

I have a errorclose_mc button in the error mc (alert_mc) that I want to remove the parent MC (alert_mc)

The code below returns the error: 1120: Access of undefined property alert_mc.