Unless it stopes you on the computer by saying some of the meida you slected was invaled there was an error with your transfer witch could be caused by transfering to many files at once.
Try yor transfer again with only one file at a time.
I havent installed WMP11 yet so I don't know if the problem is there. I'm using WMP10
This same problem has happend to me on many times and re-doing the transrers one at a thme always worked.
My only problem now is I think I put so much music on the x-box that the artis info dissapers when using the program I mean a lot of music the hand drive only has 874 blocks left.
Also if your still reading unless youre using the songs on the disk let the bar load all the files and remove the disk.
I've had much better sound quailty with no disk in the drive.
Looking for anime and game music to transfer chek out http://gh.ffshrine.org/soundtracks.php?r=42738