Mine does that too.
Think its normal.
It's probably because the HDD is working over time now that the game is reading from the HDD and saving to it at the same time.
These to responses seem to be more of what i was posting about. Ill try deleting my ghost' saves when i get home. Hopefully that helps out.I was having this problem too, and it seemed to get longer and longer.
Untill i deleted the ghosts save.
Since then it still saves the ghost information but does it smoother, without the few second freeze.
if you don't mind loosing your ghost information, Try it.