startDrag disabling buttons?

I’ve search these forums and google, and i couldnt find an answer to my problem. I hope someone here has an answer.

I’ve got a mask. Its a movieclip and inside is two movie clips in one layer. One is a large block (the actual mask) and the other is just a verticle line. On this layer has the code: startDrag(mask,true, left, top, right, bottom);
where ‘mask’ is the instance name, and all else after ‘true’ are variables defined at the root level detailed below.

now, at root level, the mask movieclip has the code:
onClipEvent(load) {
top = this._y;
bottom = this._y + 600;
left = this._x - 200;
right = this._x - 200;
Ok so this has the desired effect. the Large bar masks the movieclip and moves with the mouse vertically only and stops at the true top and bottom of the scene.

Problem is, any button i put inside the movie clip being masked is rendered useless. In fact any button i put anywhere the startDrag code is active gets rendered useless.Its as if they were just movieclips instead of buttons. They do nothing. Not even change the cursor to the default pointing hand cursor. Any thoughts on this? Please help me.