I'm in exactly the same position, though I have a lot more mods installed. For me, the whole Dawnguard quest doesn't register at all, even though I've had a few random encounters and seem heard the guard prompt (no map update). It seems to be set a stage 110, and even when I've set it to stage 180 via console to complete it, it's only actually completed a couple of times. Even then, nothing registers in the Journal, and although Fort Dawnguard is shown on the map, Dayspring Canyon isn't. Talking to Durak does nothing. When I enter the Fort, the two guys just stand there looking at each other without saying anything. When I talk to Isran he goes through the dialogue, ends with the line SirPandaFace mentioned and then they just walk off. I've tried coc-ing to Dimhollow Crypt, but it is in it's pre-quest state (wolves). Driving me nuts. I will have a go with the unofficial patch, and see if that changes anything, but I'm not holding my breath... EDIT: Uninstalling every mod made no difference, so I decided to delete every trace of Skyrim from my computer and completely reinstall. A pain, but the quest now starts correctly...