Comment 27 for bug 428306

Sounds like the same underlying issue as bug 427028. AFAICT, Ubuntu updates change the on-disk location of search engine description files, and the search service doesn't deal with having its files moved out from under it. In this case, search keywords and other metadata are associated with the path to the file on disk when that file isn't in the profile or appdir... I'm not sure why that's the case for Ubuntu's shipped builds.

Would be nice to figure out what the exact issue is, but I don't know anything about how search plugins are shipped in Ubuntu builds.