I have the same problem with my 861...downloads get to 50% and then there is an apparent timeout problem when the reset happens.
If I keep trying it, including reboots and power cycles of the 861, eventually I manage to complete the download. But it is ALWAYS frustrating and time-consuming. I avoid making any changes to the system for this reason.
The idea of configuring your system via software is great. It shouldn't be that hard to write a reliable downloading program.
BTW, I would really like it if my 861 was addressible via TCP/IP. Serial cables are passe...come on, Meridian, this would work much better if we could upload/download via Ethernet.