I am trying to get to a
movieclip nested inside a movieclip in As2:
MovieClip1, MovieClip2, MovieClip3 is instances Names.
Your approach is correct. Based on the change in spelling between the two lines you show, if you are having a problem, that may be the cause.
What he is trying to say is you should check your spelling, watch out for capital (big) letters, check if it's movieClip or MovieClip...