I filed both EB1b and NIW in oct, 2006. The EB1b case was approved soon at TSC in the end of oct, 2006, then I filed my I485 based on the approved EB1b 140. In Oct, 2007, my I485 case was transfered from TSC to NSC. My NIW case is still pending now at NSC, and RFE was send out Jan 30, 2008.
Today, I called the NSC and was told my I485 was pending due to the pending NIW petition. They are waiting to make decision for my I485 until my NIW I140 is approved and the approved I140 was automatically canceled.
My lawyer suggested me to withdraw the NIW, or wait until NIW is approved, so that the USCIS can process my I485 case.
It seems that it is better to withdraw NIW if you have EB1 case approved.