Same problem here. I began experiencing this problem with not being able to download songs (with a Zune Pass). I did the DRM system reset per Rajesh (Zune Product Team) - see this post: http://forums.zune.net/0/1/394603/ShowPost.aspx#394603.
Now, not only can't I download songs, but all the content I've already downloaded won't work (gives me the same error). The cure is worse than the disease??? Geez, what a Monday!
Here's the error message (which, when you DO click "Web Help", returns this message: "Unfortunately, there is no specific Web Help message for this error yet." That's real helpful.): "Can't verify your media usage rights. A local firewall might be blocking access to the Zune service. Check your firewall settings and restart the Zune software. If the problem persists, click Web Help. Error Code: C00D12F6"
P.S: When I right-click on a song in the Zune software and select "Properties", DRM shows "Yes - invalid license (has no usage rights)". I think NOT!