Firefox 2.0 is hanging

I tried to look at java version at www.java.com/...
By pressing the button "Install Missing PlugIn" the Browasr is standing. By moving the mouspointer or mouse klick the Window is going on a step.
If ei want to get something loaded I have to push the mousbutton or move the mouse.
At a second try (after 20 min.) of the same thing all looks normal. By restart Firefox the same "hanging" happens again.