Attempting to view any applet from Internet Explorer using the Kernel JRE causes the browser to immediately crash. This is evidently caused by interaction between the new plug-in and Kernel, as Firefox (which uses the old plug-in) works fine. It fails even if all of the bundles have been downloaded; the determining factor is whether or not the JRE has been completely reassembled.
There were two issues:
1) The new plug-in was looking for "client" and "server" JVMs, but not "kernel".
2) There was a race condition with the "initialized" variable in Java_VM.c. Presumably the fact that Kernel was having to perform a download, and thus dramatically altering the timing, was causing this to manifest.