I got the LUD's on my 2nd 131 for 7/22/07 also. I think they have this mass update program that runs during the weekend that Updates the dates to the files that were handled during the week....who knows what happens there..Such a black hole.. We can keep guessing for our amusement..for all they care.
I also mailed my 4th EAD application over the weekend. USCIS is milking me for all I am worth
I just checked my online status and I have seen LUD's on our I-131's which were approved in 2005. Something going on, let's see what happens, we should not worry too much on this stuff, whatever should happen will happen, we are unncessarily looking into that too much.
As per my understanding they are trying to move all the old cases to Ironmountain, who will store the information in a very secure and protected area and maybe USCIS doesn't want to keep all the old cases with them....