I-140 updated a couple of days ago, what does it mean?

My I140 (NIW-NSC) was approved in 9/2005. My I485 has been pending since May, 2005. A couple of days ago, I found my I140 was updated again without any information change for the online status. There has been no update for my I485 since last Aug of 2006. Does any one have same experience? What does the I140 update mean? Thanks.