Without knowing what "the lines" are that you wrote, no one could tell you if there is a problem with them specifically. What we can tell you, is that mIRC itself doesnt play the sounds/mp3, it just sends the command to windows, which then kicks it to mediaplayer. So, its possible the problem is within your mediaplayer codecs. Several ppl have reported probs with those. Try the search feature, expand the date range a good bit and use terms like mp3 or codecs as there are several threads on this.