I have completed the quest Horn of Jurgen Windcaller, which is needed for the Cultists to attack you. The boat didn't appear before or after the quest was finished.
I've installed it exactly the same as the Dawnguard DLC which is working as I have the quest for that.
I have the most recent patch for the game 1.9, I installed straight to that (I assume it installs all the prior patches as well since Dawnguard is working.)
I have it listed in the Plugins.txt document with all my other mods/dlc with the .esm being over the .bsa file. And all the DLC/Mods are in my data folder.
Not had any errors at all with anything else, everything seems to work perfectly.
My Mac OS X Version:
Mac OSX 10.8.3
My Mac Model, GPU & CPU:
AMD Radeon HD 6750M 1024 MB, 2.2 GHz Intel Core i7
Edit: I appologize. I should have put a bit more effort into fiddling with it myself. I fixed it by removing the Dragonborn.bsa and Dragonborn.esm files to my desktop, deleting the Dragonborn.bsa/esm lines in the Plugins.txt file. Waited about a minute and placed the files back and readded the two lines with .esm being top as usual but now with the Dragonborn part being at the bottom under my mods. Feel silly for this post now but if anyone happens to search here with the same issue they'll have a solution.
Edited by DuoVandal, 10 April 2013 - 06:32 PM.