A fuel stop on a 763 going transcon? No way. I bet it's a timed-out crew that needs to swap out. If you look at the differences between departure times as reported by DL.dumb and FlightAware, that looks like about a 2-hour taxi out. That might just be enough to time out the crews.
DL8878 is diverting to SLC and DL8877 is diverting to DTW. These are staff & cheerleader charters, I believe.
Not surprisingly, our friends over at A.net are discussing this too:
http://www.airliners.net/aviation-fo....main/5986372/