Looking at the IHWP variable for the end of run files for 23597/4675 and start of run files for 23598/4676, the HWP was switched between the runs as Ryan's log entry indicated. Also the auto log of the HWP settings in the post below also indicates it was flipped around 11:30:
http://hallaweb.jlab.org/halog/log/html/1204_archive/120419044708.html
This also indicates it was put back IN a bit after 4 AM.