Start procejt with mc._invisible then make it visible by button, impossible? :

Question

Hello, like topic reads.
Iv googling and trying to make my movieclip invisible from start and then make it visible as you hover over a button. It seems impossible. You make it invisible and when making it visible again it just flickers and dissappears. 
Simply putting mc._visible = "false" in the code
and then putting this on the button:
on (rollOver) {
mc._visible = "true" }
WONT WORK.
So if this is impossible, please just tell me and I will simply just skip the idea of having speech bubbles entering on rollover.  : )
and btw, sorry if I come off as arrogant, ignorant and stupid.
Im just so frustrated at the moment, I have spent 3 hours on something that initially I just wanted to add as a little nice detail.

Answer 1

that should be:
mc._visible=false;  // no quotes
on(rollOver){
mc._visible=true;  // no quotes
// or, even better:
yourbutton.onRollOver=function(){
mc._visible=true;