When you removed the HDMI cable from the cablebox, did you unplug the actual cablebox after? With a lot of cableboxes, if you don't power cycle them, they still detect the HDMI and the Selectable Output Control software does not disable itself.
From the sound of it, I would think this is SOC and the HDMI may still be the problem. If not, you've already tested and replaced the component cables, so it is still possible something has shorted out within the video outputs.
I hope this helps!!