The automatic installation of JDK6 on our Hudson box restarted the computer without any prompt or warning. This was quite unfortunate as the box is a (hefty) server hosting a bunch of services and some other VMs.

Log Output From Build with JDK install:
[SNIP]
Choosing the download bundle
Downloading http://cds.sun.com/is-bin/INTERSHOP.enfinity/WFS/CDS-CDS_Developer-Site/en_US/-/USD/VerifyItem-Start/jdk-6u20-windows-x64.exe?BundledLineItemUUID=xaCJ_hCyJigAAAEo3hNwTb0p&OrderID=UNKJ_hCyTdkAAAEo0xNwTb0p&ProductID=XgFIBe.o09gAAAEnWjJHqPYe&FileName=/jdk-6u20-windows-x64.exe
Installing J:\DevTools\hudson\tools\JDK6\jdk.exe
[JDK6] $ J:\DevTools\hudson\tools\JDK6\jdk.exe /s '/v/qn REBOOT=Suppress INSTALLDIR=\"J:\DevTools\hudson\tools\JDK6\" /L \"J:\DevTools\hudson\tools\JDK6\jdk.exe.install.log\"'
[/SNIP]

Windows Event Log Entry about Reboot:
The process msiexec.exe has initiated the restart of computer TEMPEST on behalf of user NT AUTHORITY\SYSTEM for the following reason: No title for this reason could be found
Reason Code: 0x80030002
Shutdown Type: restart
Comment: The Windows Installer initiated a system restart to complete or continue the configuration of 'Java(TM) 6 Update 20 (64-bit)'.

How This Made Me Feel:
Sad.