I'm a big fan of the Javadoc Search Frame userscript. Today's apperent outage of the Javadoc page has forced me to use a local copy of the documentation. I did some poking around on the Greasemonkey mailing list and found that if you still want to run this userscript (or any other userscript) on local files, you will need to edit your about:config. An update changed the default greasemonkey.fileIsGreaseable in about:config from true to false for security reasons. If you want to run Greasemonkey on local files, simply change that value to true.
Also, if you're using the shiny new Scriptish, the value to set to true is extensions.scriptish.fileIsGreaseable.