Get an HTML with an entry: Open Mozilla preview. The dialog box is shown. The text is like: "Cannot load class sun/plugin/JavaRuntime Bridge was installed to (here path to installed jre1.6), but the class is not there. Correct registry key: HKEY_LOCAL_MACHINE/SOFTWARE/JavaSoft/Java Plug-in or correct your CLASSPATH." On next mouse move IDEA crashes. I have not found anything specific in my registry, just paths to JREs: 1.3.1_16, 1.5.0_08, 1.5.0_09, 1.5.0_10, 1.6.0. IDEA is installed from EXE installer, Mozilla preview was automatically downloaded on IDEA's demand. Firefox does not crashes when opening this file independently from IDEA. The essential point is "java:" entry in classid value. When changed to anything else, e.g. "vava:", crash does not happen.