I just recently decided to switch to the [http://nightly.mozilla.org/ nightly build of Firefox] and Java seems to be having a problem with it. Before anyone asks, This is the Java version I have (straight from "java -version"): java version "1.6.0_26" Java(TM) SE Runtime Environment (build 1.6.0_26-b03) Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02, mixed mode) When I installed the plugin for my x64 Java to Nightly all seemed to go well. I restarted Firefox and opened up the test page for Java... during which the browser crashed without any warning nor error message. When I reopened the browser it started without even hinting that it had crashed just 20 seconds before. I followed the steps on [https://support.mozilla.com/en-US/kb/Troubleshooting%20plugins this troubleshooting guide] and found that it was indeed the Java plugin that was causing the crash so I followed directions on the same page to uninstall the plugin. When I went back to a page with a Java applet in it, the browser correctly asked me to install the missing plugin, but when I did it said that there was an error doing so, stating the plugin was already installed. I'm at a loss for what to do next because Firefox does not say it has any plugin for Java installed yet the error when I try to install the plugin states that it is installed.