Problem(s) Encountered:

At the beginning, the guide camera would not stay connected -- it would drop out after maybe 30 sec or less, but could be restarted by disconnecting and reconnecting using the setup buttons in Maxim DL.  Eric suggested cycling the power on the USB extenders; I did this and the problem did not recur. (I also unplugged some connectors and replugged them, and removed power from the camera for a bit.  Any of these might have done it in principle.

Solutions:

I believe the power cycling and reseating connections on the USB range extender was the solution.  This problem used to be more typical with the Andor CCD at the 1.3m as well.  I purchased a more robust range extender for that system and the problem has gone away completely.  At >$330 a pop, I wanted to verify the component before purchasing more, but it sounds like that time has come.  

Incidentally, this problem seems to be more an issue at the 1.3m than at the 2.4m, likely because the cable run at the 2.4m is shorter than at the 1.3m.