Comment 3 for bug 452151

So I have experimented and found that opensearch was not finding the location of the search plugins. I copied the search plugins from /usr/share/firefox/searchplugins into /home/xxx/.mozilla/firefox/xxx.default/searchplugins and it could find and use the plugins.

I first tried to just add a link to the folder /usr/share/firefox/searchplugins and the only searchplugins found were the plugins directly in the folder /usr/share/firefox/searchplugins. These are the launchpad related search plugins that ubuntu has pre-installed. The usual firefox search plugins (google, yahoo, etc) were located in a subfolder /usr/share/firefox/searchplugins/en-US . These search plugins were not indexed by gnome-do.

So it does not seem to be a real bug with opensearch plugin but rather a change in where firefox (or ubuntu) is putting the search plugins.