sector boundary errors have to do with each track at 16bit/44.1 khz having the exact number of samples (it's a multiple of some number and not really relevant). due to the 44.1 sampling rate, not all programs cut the tracks with the proper number of samples. cdwav automatically cuts on sector boundaries. there is a way to make wavelab cut on sector boundaries, by choosing the right type of marker. I think it's called a "cd track splice" marker or something like that. if you sink those markers instead of the generic yellow markers, you should be able to use wavelab to cut on sector boundaries. tracking in cdwav is a lot easier though, and if you are ultimately going to be using flac anyway, you can output directly to flac and skip the individual wav track step.