After installing ISA, was unable to use RDP to access the server.  A search of "can't rdp into ISA server" produced an obscure article about enabling RDP access on multihomed servers (servers with mor than one NIC).  It turns out that using ISA to publish RDP access servers and allowing the internal local server RDP access on the public NIC card causes some confusion, preventing RDP access to the ISA server only.
To correct this issue, on the ISA server, modify the terminal services configuration>connections>properties>rdp-tcp>properties>inerfaces
enable terminal services on the non-public interface.

This will not impact published client access