I am experiencing the same problem. We have 2 replicator2 machines. Both will successfully start a print but stop pat way through. The printer head stops extruding but continues to go through the motions. These are parts from a file I have use successfully in the past a number of times. I am printing PLA at 230C. It appears that at some point the pla is getting stuck in the feeder tube that screws into the heater block. Yesterday I dismantled the head. Cleared out the feeder tube and the extruder tip. Readjusted the build plate. The print started beautifully but stopped after 3mm had been put down. This was a 16 hr print. It was running around in the air when I came in this morning.
Puzzling and pretty frustrating.