A minor update to fix the way Zune Software treats metadata (artists, albums, genres etc) was released yesterday. This is for new installations only, its not an upgrade; if you already have Zune v2 installed, here is a support article to guide through the process of fixing it by yourself...
From ZuneInsider :
Just spoke with our Dev Team, and we’ll be issuing a small software update today. There are no features in this update, but it does help users who haven’t upgraded yet avoid some metadata issues that we’re reading about in the forums.
If you’ve already upgraded your software, there is no need to install the new update. If you are seeing some metadata issues be sure to check here for how to address them.