OOOH yeah. Several times. Tried from before I even left Riften. Tried re-downloading Dawnguard, tried disabling all my mods, tried deleting Script Dragon and SKSE, nothing has helped so far. Seems to me that something is preventing the quest from updating, thus preventing me from continuing the quest.
I did a little more searching here on the forums and discovered someone else with this problem, but saw no solution. This could be fixed is someone knew the console command that advances the quest past this point, but Google has been no help here.
I play on Xbox so I'm not too well versed in console commands but would it be the same command you would use for any other stuck quest to push you along ? Or does each quest have a different command for pushing through ?
Hmmmmmmmmm....... I'm stumped

seeing how you re-downloaded it and turned everything off I have no clue as to what maybe preventing the progression, ( stupid question but I gotta ask ) did you talk to everyone at the start or did you take off the second you got the quest marker ? Perhaps it's a little dialog that's keeping the quest from progressing. Did everything seem to run smoothly through out the quest ?