Problem with layered masks

hi there, i desperately need your help!

i have a flash website intro with 6 movie clip buttons.
everything went well until i made those movie clips into masks.

only 3 of the masks keep working.
the other 3 show the masked picture, but refuse to react on mouse events.

each mask is on a different layer and the masked pic is in the layer that’s directly underneath. i’ve grouped them in folders too.

i noticed that the order in which i place the mask layers in the timeline affects which movieclip button masks works and which ones don’t…

other than that, i don’t have a clue u_u