A bunch of .avi files burned on DVD don't have sound when played on standalone DVD players (Sony and JVC). The same files burned through Nero from Windows, work just fine.
Same computer, same hardware, same burner.

Any idea what could be the problem?

A.

do they play on the pc?
what did you use to burn the dvd? k3b?

Yes, they do play on PC.
Yes, I use K3B

the k3b one plays fine when played on Windows using Media Player (not vlc or mplayer)? Just wondering if it's some kind of codec incompatibility that Nero compensates for.