Hey, i got the same problem but it was like the other ones. The bug issnt the quest, its the arrow ^^
I try to speak english, but sry if its bad:
1. Go back to the Tower (where was the stone with the text we copied) 2. Go out of the Tower (u are on a high point, there is a window ..left is a door) 3. Here u see the City from top, dont go to left door, go right of it 4. here u see a waterfall and a small way! 5. go through the small wall (u will see the arrow is middle of waterfall) 6. jump into the waterfall ... 7. go back to winter and speak to him 8. done :D
Hope u understand ..i can write it in german if u understand german
PS: If u dont follow the way that says the arrow, u arent able to do the quest, thats the bug...