Hi,
I've just re-read the CC2538 IDE user's guide.
My mistake was to create a project using the selection: "Empty Project (with main.c)". Even with the the device set to "CM2538SF53" this build OK but fails to load.
Following the guide and creating the project in Other Examples -> Blink LED CM2538SF53, builds and loads fine.
Thanks for the help.
Cheers, Steve