Bah, it’s a bug in Microsoft Productivity Power Tools for Visual Studio 2010. the “Ctrl+Click Go To Definition” feature. Apparently, when I click a new location and then press “Ctrl+V” – if I do it quickly enough, it interprets it as a Ctrl+Click and immediately tries to trigger a navigation, even if I clicked on an empty space. The error comes because it doesn’t know what I’m trying to navigate to (answer: I’m not).