Okay so I've gotten to the point in Dawnguard where I chose to side with the vampires, after going through the vampire lord tutorial, I get sent on a quest to speak with the Lord's person thingy ma bob to continue the quest, yet I can't carry on as everyone is hostile!? I have done nothing to them or anyone, I don't have any murders at all let alone around Solitude, they are literally attacking me for no reason.

Lord himself won't attack me, nor will his daughter or the hell dogs, but everyone else goes nuts and attacks me. Does anyone know why!? I did not pay ￡14 for this to happen...

Thanks!

Sounds like stage 4 vampirism before Dawnguard came out.
Try using that vampiric persuasion power on some bandit outside of town, preferrably lower level, and feed off them, other option is find a sleeper and drink, if this is the cause.

No he means just inside the keep itself. This was raised before, I think it had something to do with some of the spells you try in VL form during the tutorial not sure off the topof my head but just try skipping as much of it as possible see if that helps.

Do you think attacking the cattle inside the tutorial could of caused it? I've read around and apparently Duel - Combat Realism can be a catalyst in this glitch but I don't have that iirc.

Annoying as hell because I want to experience this story and nail the daughter at the end. Don't ****block me Bethesda...

It could be the cause, and I think it's just a game bug.

Okay I've gone back to an earlier save when I entered the Castle as a mortal, Duel is uninstalled and I did not attack the cattle. This time I got further into the hall and everyone was fine.

"You are a blessed sight, you are welcome he-" Then I get attacked. How could Bethesda let a bug like this slip through?

Okay, so I've seemed to of fixed the problem. I deactivated 'Duel - Combat Realism 5' 'Revamped Vampire Lord' and 'Reduced Distance NPC Greetings'. I then loaded up my Autosave from entering the Castle and did the tutorial again, this time doing nothing at all except what was asked of me on screen, did not even look at the cattle. Now everyone seems to be happy with me. I saved and reloaded right in the middle of the dining hall with those three mods reactivated and everything is still okay. I think that so long as you pass the alliance check or whatever it might be in the background, and are confirmed as a Vampire, mods should be able to work again.

Hope that helps anyone else who has this problem.

If it doesn't work, try this; http://forums.nexusmods.com/index.php?/topic/751549-dg-vampires-attack-me-after-joining-them/page__p__6001769#entry6001769