Look at Tools -> Settings -> General Section. Near the top, make sure Open Firefox automatically when your computer starts up is Not checked.

If it's already unchecked, try checking it and then unchecking it.

If that doesn't correct it, make sure you don't have a Firefox shortcut in your Windows Startup group or that it's not somehow in the Windows Task Manager's Startup tab.

Mark,

Thanks. I have unchecked the start-up box, but I will try your recheck and see. The reason I am replying now is to be sure I mentioned that I am running a IMac computer system not a Windows System if that would change your message. Thx again.