well, there are no capacitors that were affected in this motherboard blowout, so maybe it was a wiring fault where the USB cable (which led to the top panel of my V2000A case) was plugged in. the major burn area (see center of the motherboard corner image) is actually the USB jumper, which was surrounded by a "wall" of plastic.
as a side note, my onboard USB never worked, and there were other USB ports throughout the rest of the motherboard with the same problem. i had to purchase a third-party PCI card to get USB connectivity, which sucked. i doubt this had anything to do with it, as i hadn't touched the mobo in perhaps a year or so and the USB had been plugged in that way for the entire time.
i'm still planning on leaving my computer on 24/7, although i'm a bit scared. however, i'm not going to ignore what happened last night because that would just be dumb. i think it would be a best to get a smoke detector near my computer. that's what i plan to do for the future, since i don't want to end up killing myself one day due to another computer electrical fire. i suggest you all do the same if you have the same reservations.
if anyone has any ideas about where to purchase a small-sized smoke detector rather than those larger ones that go on the ceilings, please feel free to share it with me and the others. 🙂