Saving a job configuration results in "HTTP Status 500 - java.io.IOException: Unable to delete C:\.hudson\jobs\example-project\config.xml" when "Do not save duplicate history" is selected.
To reproduce: go to "Manage Hudson"
>"Configure System">"Job Config History"->"Advanced" and select the "Do not save duplicate history" box. All other configuration settings for the plugin can be the default values. The error occurs whether or not there are configuration changes, so just going to the config page of a job and clicking "Save" should result in this error.
I'm surprised that no one else has come across this same problem, so I wonder if it's particular to my setup. I would investigate further, but I haven't got the time right now. Hopefully, someone can take a quick look and at least determine if the bug is reproducible.
P.S. Thanks to Stephan and Mirko for the handy plugin. This will help clear up a lot of confusion about who changed what in job configurations.