after 3 days and trying everything to solve the audio sync problem i have finally done it with PERFECT RESULTS.
i tried everything, older versions of Nero, VirtualDub etc etc etc.
tehn i saw another posters suggestion and put it to the test.
this works for Nero 6 vision express all versions.
DISABLE THE Nero CODECS
its that simple, once this is done you will be able to make dvd's from avi's without the sync problem.
how do you do this.
1.remove your digital serial number. (make sure you keep it somewhere to re enter later)
put your pc's date forward 1 month so the codecs expire.
use Nero vision express, it will now work correctly.
when done, put your serial number back to you can use recode and other things that are disabled when you remove the serial. also dont forget to put the clock back to the correct date.