If it is your only I-485 with USCIS pending, it will be a mistake made by them when you receive I-765 approved w/o fee.
http://blog.wenxuecity.com/blogview.php?date=200706&postID=42162#noFee
http://blog.wenxuecity.com/blogview.php?date=200706&postID=42162#noFee