Are you setting this data inside Constructor or function?
EDIT:
Hm, where to start...
1) You know that the trick with static is not gonna work if you'll create more than 1 instance of class? In this case if you have only 1 Main class it's gonna work, but omg... Imho it's not nice to store data in static vars...
2) If you already declared:
public var bynavntxt:TextField;
public var intervall:TextField;
later just do
bynavntxt = new TextField() ;
intervall = new TextField() ;
no need for type in there.
3) Later in Main you have something like:
var mcOut = new OutCursorClip();
this.addChild(mcOut);
var mcIn = new InCursorClip();
this.addChild(mcIn);
Why are you declaring new variables with same name but without Type?
Waaaaaay up you have:
public var mcIn:MovieClip;
public var mcOut:MovieClip;
so those variables are already declared. By declaring them once again you are creating local ones. Beware!! The ones from the top would be null after that.