Trouble Converting MKV to VOB file.

I have a series in mkv format I had downloaded. All of the sound works correctly when I play it in that format. I downloaded Xilisoft Video Converter Ultimate 6 and am trying to convert the files to DVD video format/VOB format. When I look at the preview screen to see what the output will be, the audio is high pitched chipmunk voice and not working correctly. Out of 12 files/episodes, 1 and 2 work and 9 and 10 work. The rest have an audio issue once converted. It seems like it may be the MKV files, but if that's the case, how come only a select few will sound correctly once they are converted? This problem has me completely stumped. Does anyone have any idea why this is? Please some one help me with this.

only thing i can think of, is to try another program to do the converting, did you try devede?