Frequent LUD of I-485

I submitted I-140 and I-485 in August, 2007. I-140 has been approved. Recently, I received a RFE for my I-485. All request document was sent to USCIS last week, then I received a notice on April 24 saying that document received and the case has been resumed.

However, I got LUDs everyday after April 24. Anyone knows whether this is good sign or bad. Thank you a lot!