What is this icon that has mysteriously appeared in my Mac OS 10.6.8 menu bar, and how do I get rid of it? The icon has a fluorescent green circle on it, here is a link: Screen capture. It is the first one on the left.

Mac OS 10.6.8

Hovering over the icon = spinning beach ball

The only utility I use is Cocktail, but I cannot find anything in the application that would trigger this icon to appear