Disaster strikes musician!

Whilst moving some plugs around on Friday night, I went to turn on my audio
computer and a blue spark flashed out the back. The computer did not turn
on. For some mad reason I decided that I would try a ANOTHER power lead
(which turned out to be a 13amp fuse). Then there was a REALLY big yellow
flash when I went to turn it on and the power tripped out at the main board.
I don't understand why the computer would suddenly flare up like that. I was
having no problems with the combination of plugs and wires before, though
maybe I overlooked something this time round.

Any theories as to what might have occured?

Thanks in advance.

Andreas