Won't start when "hot"

Truck starts just fine, actually much better now with the MSD digital ignition control, etc. What has happened before the MSD upgrade, and continues to happen, the truck won't start after engine has warmed up and has been run for 15 minutes or more. Symptoms - turn the ignition and nothing. No clicking, no turnover. The battery light on the dash lights up. Almost as if it's in gear and safety "switch" is active. After waiting upwards of an hour the truck will start just fine. This is now happening on a regular basis. Not sure if the ignition switch is bad, or what I should look at. It was suggested to just replace the switch, as well as look into a "high torque" starter. So, advice is certainly welcome!