Just to confirm - the discs that you have tried are brand new blanks, not erased RW discs, right?
The most common reason for this would be other burner or media watch software taking ownership of your burner, causing OneCare to not be able to see the discs for writing. You can contact support for help with this:
Support for v1.6 is via the information here - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=1183038&SiteID=2
-steve