The all new, Firefox 2.0.0.1

About three days ago I let Firefox update itself to 2.0.0.1, and since then I've noticed that now my anti virus takes way longer to scan the whole computer than it used to.  Now it takes perhaps 60% more time than before.  Other goodies have also started to misbehave, like my Serial-to-USB adapter, sometimes stops working out of the blue and the only thing that brings it back to life is rebooting Windows.  Annoying.