I uninstalled and reinstalled flash and restarted the browser a few times, and it finally started working again. I have no idea why it wasn't working before.
This highlights one of the big downsides of this technique: LocalConnection is really flaky even on the best of days, so people may have to reload; there's also a limit of *8* localconnections on firefox: http://advision.webevents.yahoo.com/cm/LCtest/ Playing with this page, it seems that closing the page containing the communicating gadgets does not free up the localconnections either, so you have to restart the browser; perhaps that's why I couldn't get this to work earlier. http://codereview.appspot.com/116048
