So I've noticed this bug for a while. when you visit somewhere where there is a dragons corpse it often isn't in the same location anymore.
It wasn't that big of a deal to me until this happened [SPOILERS]

I killed Paarthornax and some time later (about 10 hours of gameplay) I decided to go to Riverwood. This is what I found on the road leading into town.

http://s975.photobucket.com/albums/ae234/Dakodab/?action=view¤t=ScreenShot3.jpg
http://s975.photobucket.com/albums/ae234/Dakodab/?action=view¤t=ScreenShot7.jpg

His corpse somehow traveled all the way from the Throat of the World to Riftwood...