When i start the game with dawnguard, i can play. But when i add Heartfire, the game load, show the initial image and return to windows without message at the load of main menu. I have the steam version.

In a text file :

SGeneralMasterMismatchWarning=One or more plugins could not find the correct versions of the master files they depend on. Errors may occur during load or game play. Check the "Warnings.txt" file for more information.