Well... It would be better for me to check your .fla, but you can try the following:
On the first frame of your movie, set a variable, something like:
_root.current_selection = "";
And then modify the script on your first button somewhat like this:
on(press){
if (_root.current_selection == "first"

{
stop();
} else {
gotoAndStop(x); // x being the targeted frame
_root.current_selection = "first";
}
}
On the second button...
on(press){
if (_root.current_selection == "second"

{
stop();
} else {
gotoAndStop(x); // x being the targeted frame
_root.current_selection = "second";
}
}
Etc... Etc... For all your buttons on all frames.
You can change "first" and "second" by whatever you like, like "news", "info", "contact" etc... Maybe better describing the frames the user ends up on.
Voilà!
Regards,
If you can't get it to work, e-mail me your .fla, at oldnewbie@hotmail.com, I'll insert the coding, and send it back to ya!