[media]http://www.youtube.com/watch?v=sOwAi8PzCl4&[/media]
Happend to you?
Please help me, since I can't continue..

I'm new to the forum also, so I can't seem to get the media thingy to work :/

It is a known bug I think (http://www.uesp.net/wiki/Skyrim:Alduin%27s_Bane)

Try reloading or not moving the camera when you goto the past. It happened to me once and then just went away on reload. (It was very strange how they talk about what happens if he doesnt come, then say here he comes, then they just sit there waiting forever)

Also try reading the scrolls a couple times away from the mountain (makes your character temporarily blind for a second or so) If messing with the quest like that doesn't work you can always just force it ahead with,
setstage mq206 70 (To give you the shout)
setstage mq206 100 (To bring you back to the present)

(I think you should use these in the correct sequence and during the flashback as these are not reverse-able and things can break easily)