When it comes to some hard bugs that only Microsoft's Zune team can fix the issues, https://connect.microsoft.com/
is the right place to be and ask the questions.
First step is to sign in, register, then start posting the bugs. In my case an example, I just posted that the new album by Sade "Soldier Of Love" has all kind of bugs, all ten songs skip.
At this moment, there are three people (included me) that have posted the same issue.