When trying to burn from cuesheet using Nero's (ver 5.5.7.8) FILE - BURN_IMAGE command I was sometimes getting the error message "can't open the file .... .wav". Solution - This appears when the file is still open in another application, it happens with both CDRCue and CDWave cue sheet editors. Earlier posts, about other cue-sheet problems, gave me some clues.
Thios also happens then the file is not located in the path written in the .CUE file after the FILE tag.