Hi Tom, did this just happen out of the blue? Please elaborate on what you were doing before this happened.
Interesting, In that case I would advise the following:
1. First, try to unplug the CMOS battery and then put it back in to reset the BIOS. If this doesn't work, then it's likely a fault with the motherboard or the bios.
DISCLAIMER: Before you do these, check out what others around here have to say, as many know more than I do.
2. Try to make some measurements with a multimeter to identify any shorts. I would advise you to attempt to use a thermal camera if you have one around. If you don't then there's always apps for mobile devices of all kind to compensate for that! Once you identify what part is shorting the board out, let me know and we can proceed from there.
3. This is less likely, albeit a little (somewhat) simpler. Your BIOS chip could be very well corrupted, and in that case you'd need to write a new BIOS to it. This can be done Via a bios reader. Once you have that, you will need to backup the contents just in case, then write a new bios to it. Once done you should be fine to reinstall the chip.