Jeff,
Two things are wrong:
you forgot a component (you use R2 but don't specify it)
components = {"S" \[Element]
"Modelica.Thermal.HeatTransfer.Sources.FixedHeatFlow",
"R1" \[Element]
"Modelica.Thermal.HeatTransfer.Components.ThermalResistor",
"R2" \[Element]
"Modelica.Thermal.HeatTransfer.Components.ThermalResistor",
"T" \[Element]
"Modelica.Thermal.HeatTransfer.Sources.FixedTemperature"};
and 2. You got the port names wrong for the heat components:
connections = {"S.port" \[UndirectedEdge] "R1.port_a",
"R1.port_b" \[UndirectedEdge] "R2.port_a",
"R2.port_b" \[UndirectedEdge] "T.port"};
Now it works (although your model has 2 sources connected with resistors so it does not do anything interesting -- I assume you were just trying to get a simple example to work)
The error message is not at all helpful so I will report it to Wolfram in Sweden so they can fix it.
I found the best way to get started is to go into SystemModeler (WSM) and view the components there -- even create a basic model and then change/update/recreate it in MMA once you have the component names and ports correct. You can also build a simple model in WSM and do this in MMA to get the correct syntax (essentially reversing your process):
model = SystemModel["Model1"]
comp = foo["Components"]
conn = foo["Connections"]
This will give you the strings you need for the component names (or just hover your mouse over the output objects)
comp //InputForm
Regards,
Neil