Frostsaber Mount / Help?

Hello,
I've got a problem with my Human Warlock. I created the character as a Horde Undead and changed Factions some months ago.
Now I was about to grind the Reputation needed for the Frostsaber Mount. But I guess, because I used to be Horde, I cannot accept the Quest given by Riven Frostwind

It's bugged. There are six reports regarding the issue on Bugtracker (The latest report was created two weeks ago). I suggest you check it and upvote the report with highest priority.