Converting AVI to DVD using Nero Vision Express 2

I am a bit new to all this so any help appreciated!
I am using Nero Vision Express 2 to make a DVD-Video…I have no problems when adding and burning MPG vide files and can create a DVD with menu selection screen. However, am having problems with some AVI video files - I can convert burn them OK to DVD with menu selection screen. These play OK using Poeer DVD on my PC…however, when I try playing them in my DVD player (Sony D950G) I get the menu screen displayed but nothing happens when I try playing by selecting the menu icon. It’s strange as I have some other AVI video files and it works OK for these… Any ideas?