Quote (Phantom132 @ 30 Jun 2012 03:18)
for anyone that has or is thinking of getting dawnguard, watch out. downloading the dlc will prompt vampire attacks on the cities, normally this wouldnt be a problem since the guards will kill it, but theres a chance it will spawn a mysterious vampire. the mysterious vampire will sneak around in the city and kill a random npc in their sleep, in their shop, in their home. the only way to stop him is to find him creeping around, but you wont be able to do this everytime and any non immortal npc is at risk of death from it. the vampire attacks on the towns will happen no matter which side of the questline you choose
also, when you have an npc named serana following you around, theres a little glitch that makes your player character weak as fuck. so if shes in your party try to ignore battles
This happened to me while in Dawnstar. I quick traveled there and poof 2 master vamps and 1 fledgling show up and kill the blacksmith and his wife. Pretty agitated by it. And yea.. my advice would be, travel to the nearest location, kill any spawned vampires then enter the city. Unless you play using fireballs.. then incinerate 'em.