See thread http://forums.java.net/jive/thread.jspa?messageID=246583
Enabling the HTTP cache (steps outlined in thread) results in default apps for
the virtual hosts on the app server being forgotten.
They will be remembered again on stop/start or by setting the default app to
null, then setting it back to the app again via the asadmin GUI. I've noticed
it effecting virtual hosts that have a default app assigned out of an EAR.