MattCutts - 9:46 pm on Jul 13, 2010 (gmt 0)
Hey everybody, I asked folks who would know about this. It turns out there was an issue a couple weeks ago where some code got refactored, and the refactoring affected referrers for links opened in a new tab or window. Right now the team is expecting to have a fix out in the next week or so. Hope that helps.