The first downloaded video usually doesn't have sound and requires me to download it for a second time to solve the problem. But when the sound is OK the video can't be forwarded. This kind of problems do not occur when using other downloading software. Would you please have a look at it? (Take the above link for example).
What version of Mass Downloader do you use? You can download the latest one from:
and the player: http://dl.baofeng.com/storm3/Storm2009-1028.exe
but I suppose any player can forward it as long as we use the download software above mentioned.