When the Java Plug-In requires Kernel bundle downloads in order to start, it (and consequently the entire browser) will crash if those downloads fail.
The easiest way to reproduce this is:
1) Set the registry key HKEY_LOCAL_MACHINE\Software\JavaSoft\KernelDownloadURL to a nonexistent url like "http://dgayqasdf.com"
2) Install Java Kernel.
3) Attempt to run any applet.
4) You will receive a number of errors complaining about being unable to download bundles. If you have a choice, cancel them.
5) If the browser doesn't crash immediately, try shutting it down. It should crash while exiting.
Tested using IE7 on XP SP2.
(Don't forget to remove the broken registry entry when you're done testing, or Kernel won't work)