Can't get sound with imported video NVE-3

I used Nero vision express to import video from my sony digi-camcorder and then burn dvd’s with no problem until now. The last one had no sound in the middle 1/3 of the dvd. Now video is no problem, but no sound accompanies it.
The sound is fine on the tapes and plays fine when connected to TV. No error messages come at all.