I am trying to update a Hudson installation to 1.330 from whatever version was
current as of mid-August. While Hudson will start up fine after deploying the
new hudson.war, I am unable to update any plugins using the Update Manager.
When I try, they all end in error. Here is an excerpt from catalina.log:

Oct 28, 2009 2:14:58 PM hudson.model.UpdateCenter$DownloadJob run
INFO: Starting the installation of Mercurial Plugin on behalf of bshows
Oct 28, 2009 2:14:58 PM hudson.model.UpdateCenter$DownloadJob run
SEVERE: Failed to install Mercurial Plugin
java.io.IOException: Installation of plugin from
https://hudson.dev.java.net/files/documents/2402/144520/mercurial.hpi is not allowed
at
hudson.model.UpdateCenter$UpdateCenterConfiguration.preValidate(UpdateCenter.java:583)
at hudson.model.UpdateCenter$DownloadJob._run(UpdateCenter.java:846)
at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:951)
at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:832)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)