This could be side effect of FIU dialog FIX. I could reprodcue this issue with Auto and Manual update both type. During auto/manual update all the known JRE's JAVA process should be exited gracefully.

How to reproduce this issue

1. Install test jre version 6u18. Make sure JRE is installed properly.
2. Set up the UpdateServeltURL in the registry.
[HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Update\Policy]
"UpdateServletURL"="http://j2se.east.sun.com/arc/1.6.0_18/nightly/2009-09-29/windows-i586/map.xml"
3. Launch the jusched.exe, wait for 6-8 minutes till update balloon is shown in the system tray.
4. Clcik the update balloon and proceed with the installation.
5. Verify File In Use dialog is not showing up during update.
6. VERIFY JRE 6u19 is now installed, java -version has right version info
7. Uninstall the Updated JRE make sure there is now issue while uninstalling
8. Install 6u18 JRE again

Expected Behavior:
JRE should be resinstalled without rebooting the machine.

Actual Behavior
Error message with error 25025 ...need to reboot the computer...". For More info please see the atatched image.

It looks like while updating the JRE following files are locked. Checked the PendingFileRenameOpertaion reg value

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager]
\??\C:\Program Files\Java\jre6\bin\ssv_patch.dll
!\??\C:\Program Files\Java\jre6\bin\ssv.dll
\??\C:\Program Files\Java\jre6\bin\jp2ssv_patch.dll
!\??\C:\Program Files\Java\jre6\bin\jp2ssv.dll
\??\C:\Program Files\Java\jre6\lib\deploy\jqs\ie\jqs_plugin_patch.dll
!\??\C:\Program Files\Java\jre6\lib\deploy\jqs\ie\jqs_plugin.dll