After my upgrade to Thunderbird / Iceweasel 2.0 Enigmail was no longer working (see 427591). Seems like something mixed up the versions of installed add-ons. I fixed it by removing Enigmail, starting and stopping Thunderbird and reinstalling Enigmail.
A new version of Hover is available. This release really fixes a problem with search engine friendly links. The previous version v0.6.4 only fixed part of the problem.