I have an uninstaller hang on couple windows machines. It is not consistent, but you can reproduce it.
If you check ps -ef, you can find couple process running including javaws:
.../javaws.exe -silent -shortcut -uninstall
If you kill this process (javaws.exe) uninstaller will finish with reboot asking.
To reproduce it just install and uninstall jre from nightly build dated May 02 or you can use promoted build 82.