If you switch System Preferences:General:Font Smoothing Style to "Standard" this effect goes away. Apparently "Standard" turns off sub-pixel anti-aliasing, which is where this bug must lie.
~/Library/Preferences/ByHost/ contains preference files which are tied to the primary MAC address of your system. One of these (Library/Preferences/ByHost/.GlobalPreferences.MAC.plist) contains the font smoothing setup.