Now alduin doesn't even land on the tower in helgen at the start of the game!!!The headsman just stand there with the ax high in the air whaiting for something!!
How am i suppose to start a new game now??
I tried 3 times,same problem over and over again.
Am i the only one?

Elaborate. Does Alduin just cruise around like he doesn't have a care in the world? If so, then you aren't alone, but I've had that problem before Hearthfire came out. Hell, I had it before Dawnguard was announced.

Day one glitch, not Hearthfire related. I've never experienced this myself so I can't help, sorry. I heard restarting would resolve it but you obviously tried that.

Maybe clear the cache (Hold LB,RB, and X when the game is starting up, until the "Press Start" button) and try again?

I can confirm this is a vanilla bug/glitch. Happened to me before even dawnguard was released.

I have also started a new game (as of 11:40am today). Everything executed fine on the beginning.

Ok thanks.guys.i will try again...ah and ps:fo those who have preblems with the crashes in lakeview manor due to the greenhouse,after some experimenting i think that the bug is caused by one of the barrels,specifically,the one that makes mushrooms apper under the northern display case.