Thunderbird did an update from version 24.0 to 24.0.1 a few days ago, and unfortunately that update broke binary extensions, such as Lightning and ExQuilla. This issue is being tracked at Mozilla for Lightning in Bug 925823 with a platform fix being looked at in Bug 927073
ExQuilla is releasing, for Linux only, a version 24.5.1 which provides compatibility with Thunderbird 17.*, 24.0, and 24.0.1 This will probably also work with later versions of Thunderbird, but it depends on whether Mozilla bug 927073 is landed before Thunderbird 24.0.2 is released.
Download link for ExQuilla Linux users: exquilla-mesquillanet_Linux_17-24.5.1.xpi