So I've become a VL and left Harkon's tutorial chambers. Everything is fine, Harkon, Serana and the Elf guy I have to talk to for the chalice quest are all nice. All of a sudden if I take a few steps near the main hall, every single NPC becomes hostile. I've tried console commands to add them to factions, but it didn't seem to work. I've reloaded saves as well, still no go. This is an absolutely ridiculous bug that completely halts me from playing on. I can't even exit the castle.

*EDIT* The game also completely freezes sometimes when I transform into VL. This happened twice in a row now while restarting the whole castle entrance and while about to use it for the first time. Going to sleep since I can't seem to make any progress.

If your playing with mods they sometimes conflict with dawnguard. Hope this helps.