I found that my video became crackly whenever there was background music. I couldn’t understand why because when I played it in any other player on my computer it sounded fine, only in Nero Vision Express and Nero Showtime did it all go downhill.
After trying multiple codecs and updates and even other programs altogether I was getting pretty angry.
I finally discovered that if I pay for and download an additional plug-in called Multichannel Plug-in the problem is fixed!
Hurray! It looks like my sound needed the 5.1 support from the plug-in.
I hope this helps other people because during my issues I saw many other people with similar sounding problems and I think this could be your solution. They really should provide this plugin for people with older versions of Nero and not just Nero 7.