AS3 _parent?

_parent no longer exists in as3. It is now parent and you have to tell flash that its a MovieClip (2 examples):

MovieClip(this.parent).gotoAndPlay("reveal");
MovieClip(this.parent.parent).gotoAndPlay("main");

Great articles that explain it all:
http://www.zeuslabs.us/2007/07/12/disabling-actionscript-3-strict-mode-in-flash-cs3/
http://curtismorley.com/2007/06/13/flash-cs3-flex-2-as3-error-1119/