K8tlyn, I'm having the same problem with Media Sync. It worked fine with my 9630 the past couple months, but it crashes now when I have my 9550 plugged in and launch it. I'm on Vista, so I don't think it's an XP issue. I'm on 5.01 of DM and this is the first time I've tried it since changing to the 9550. On a side note, Media Synch still says it's going to synch with the "9630" across the top of the screen even though I have the 9550 plugged in. Unfortunately, it crashes immediately so I can't go into options and check if there's a setting I need to change. I'll keep researching and report back here if I find something.
Update - OK, I already figured out the issue with it showing the 9630: http://bit.ly/6kA5Bb
Apparently that's an issue Rim knows about. But that's not why it's crashing. Still looking.
Another Update: All fixed. It could have been the sequence.... I already had my 9550 plugged in when I launched Media Sync. This time I launched Media Synch first then plugged in the BB. It allowed me to rename the media card and re-initiaize. then sync my playlists. All is well now. I also read someone else's problem was that they had some negative number of plays and negative ratings in itunes and once they were deleted that fixed their issue. Good luck.