There are threads about this all over the place.
Possible solutions I have heard of are first, convert the files using another utility prior to putting them into NeroVision.
Second was a suggestion to replace the Nero Codec with another one. Renaming the file could be tried, but I suppose you would need something installed to replace it.
zwuijs has said using a NeVideo.ax file from an older version helps (this may be for a more involved problem).
Basically, it appears the Nero Codecs can't handle certain types of files without having a audio sync problem.