This maybe due to extra, non-audio information contained in the .wav file. Here’s what Nero says about it:
“If your WAV files have been saved using Sonic Foundry’s Acid or SoundForge programs and other similar programs, the files may be no standard WAV files. Sometimes such programs save WAV files with markers inside the file. Although this never affects the replay of a file (even in Nero), Nero refuses to burn any CD with a WAV file that has these markers encoded in them.
It’s best to set these programs in a way they do not generate this header information when they create WAV files. This will help to ensure compatibility with other programs such as Nero.”