There is at least one Java related crash with the latest Firefox Trunk builds when AdBlock Plus 0.7.5.1 is installed.
Steps to reproduce:
With AdBlock Plus installed, go to http://www.java.com/en/download/installed.jsp and click on the green "Verify Installation" button.
Found the regressionwindow for the crashes with Java if AdBlock Plus installed:
Works in 20070905_1328
Broken in 20070905_1344
However, there seem to be more pages using Java that crash - not necessarily related to this bug here.