I'm using a notebook with Windows 7 x64 and Firefox 4.0.1 x86 and I used to have JDK 1.6.0.24 x64 installed, and also it's corresponding public JRE (also x64). Yesterday, I noticed that Java applets didn't work in Firefox. It asked me to install the required plugin. I did, and JRE 6u22 x86 was installed alongside. Now Java applets did work, hurray. Because I didn't want multiple (old) JRE's, I uninstalled all of them and installed JDK 1.6.0.25 with it's public JRE instead. Again, 64-bit. Now Firefox refuses to notice Java again. The plugin menu doesn't show any Java-related plugins. (Not even Java Deployment Toolkit, which used to be there before.) I have tried setting the current Java distribution as default for all browsers with the Java Control Panel, but that didn't work. Is this just because Firefox x86 can't deal with x64 plugins? Should I download a x64 build of Firefox instead? Or will that make the rest of my addons stop working? EDIT: currently I removed the 64-bit JRE and installed its 32-bit variant. Everything works again, also in Firefox. I would still prefer to have everything 64-bit though.