IGNORE THIS report. Have not been able to reproduce this since I removed free Lockdown from my Mac. It probably is Lockdown, which was causing several issues on my Mac (breaking my Personal Hotspot on ios, interfering with other VPN apps) or an Apple bug that has been fixed.
With FF 13 in the Dock clicking on it does not work if you hide FF13 and go to another program, then click FF13 in the Dock. The currently running programs at the right does work. FYI the FF13 editor works correctly with the Dock.Math meets art meets psychedelia.