Setting the menu background music audio properties

[skuppy]

Hi Guys

I am using proX8, win7 64 bit
Have created my project and am sharing to Bluray
When setting up menus I have selected my own background music for the main menu
Now I want to change the duration of that music from the default and apply fade in/out
The default sounds like a duration of about 10 secs or so
So I change the duration to what I want and apply fade in/out
But when I go to preview the video the duration is set back to the default
What am I doing wrong
Why isn't my duration change saving ?

thanks in advance
Chris