Stuck blips over PA, MD, Washington DC area

I’m noticing a small handful of blips that are stuck in the same position for the last 2 weeks or so. The northernmost is CLX779 over north-central PA, N391JA between Harrisburg and Philadelphia, N4690E and N136MA together just west of Harrisburg, N40JA and VV7E110 together just southeast of Baltimore, N5028V south of Washington DC, and lastly, N754SP southeast of Washington DC.

All of the above mentioned flights had unusual codes instead of the normal ICAO letters, and all say ESTIMATED.

Any idea why they have been sitting on the map for 2 weeks? CLX779 has been on the map for 2 weeks but newer flights using the same flight number have occured. All say they landed 2 weeks ago except N754SP, which says landed 1 week ago. Checked 2 different computers and am seeing the same thing on both the flight page (“big map”) and main page. Currently using Windows XP with Internet Explorer 8 if this helps any.