Same issue was raised in XStream's JIRA (please see the attached URL).
s from version 4.0.0, Oracle changed the Vendor name of it's JVM, Oracle JRockit. Until this point the Vendor name was "BEA" - this is for what the current 1.3.1 XStream implementation looks for while checking JVM vendors. Oracle changed this in this release to "Oracle" which now causes to fail the vendor check in XStream.
The result of this bug is that hudson starts, but instead of the welcome screen, it only shows a page that complains about XStream is not supporting this VM.