I have a MacBook Pro. Firefox is set to my default browser and there is an icon in the dock. However, whenever I restart my computer, the Firefox icon in the dock becomes a question mark. It is not clickable and does not open Firefox. If I drag the Firefox icon from my Applications folder into the dock and then click the icon in the dock, a second icon appears and Firefox runs from that second icon instead. Currently the only solution is to open Firefox from my Applications folder and then select "Keep in Dock". However, the next time I restart, the icon has once again become a question mark that doesn't open Firefox.