I'm going to disagree with Brian's assessment slightly. Melting of the wires is from too much current flow. That *could* mean a direct short to ground but not necessarily.

It just means the expected resistance in the circuit was less than specified. It sounds like a couple loads found their grounds through the ECM. Very similar to my buddies Corolla that would melt his clutch cable because of a bad ground connection between the battery and engine block.