Problem loading a SWF


Just want to start by saying I just started learning Flash and any help would be appreciated.

I am trying to load/play several SWF files with the use of a navigation bar. The buttons have the following code to open the SWF files:

on (release) {

My problem is that the images/text shown on the movie remains on the screen when the new movie is opened. So the last frame from the old movie can still be seen underneath the movie that just opened.

Is there a function to clear the screen? or does it have something to do with layers positioning?

Thanks for your help