I have suddenly developed a strange occurrence with the Firefox icon. I'm running mac OSX and have always placed the icon next to my Thunderbird icon (just for tidiness). Yesterday I noticed that the icon have moved to the end of the dock. I dragged the icon back to it's original position and for a second it stayed there, then jumped to the end again. I tried three times and it did the same thing. So I left it until this morning. But when I booted up this morning the icon had vanished altogether. I've just added a new icon to the dock, which immediately jumped to the end again. Does anyone know what is going on?