Ever since the upgrade to Snow Leopard, Firefox started to open behind other applications.  It launches from the dock normally and is the active application in the top menu bar, it’s just behind everything else.  You can click the icon again or command-tab to bring Firefox to the front, but I must say, it is quite an annoyance.

A google search revealed a mozilla support thread reporting the same thing, but at the time of this update, no replies with any details on how to fix it. See this URL.

I’ve switched my default browser back to Safari now, until a time when Firefox opens the way  it should.