The problem will all Comcast and Sprint customers is with the return trip through Savvis. You cannot see the problem on the trip from your computer.
Savvis is routing every packet out of Dallas to Los Angeles, then back to Dallas, regardless if its destination.
Refer your Comcast and Sprint contacts to
this thread. Do not let them tell you it is an AT&T problem. Your traces cannot show the problem. The return traces I have in the thread I linked shows traces in both directions. It is imperative you do not supply Comcast and Sprint with your own traces.
If you do that, they will respond it is an AT&T problem, when in fact, it is not.