I am using a development version (3.5-beta1-22104).
Somewhere along the way the body class changed and is causing issues with every theme.
home-page logged-in home blog admin-barjs debug-bar-maximized customize-support
home-page logged-in home blog admin-barfull-width custom-font-enabled single-author customize-support
Notice the admin-bar.....
There is no space after the admin-bar and whatever comes next. This happens on all themes in my system with zero plugins activated.
Whatever function is outputting admin-bar into the body tag, is not leaving a space afterwards, thus causing the problem.