Same thing happened to me. I had SL installed a couple a weeks ago using the "drive replacement" method (with SL installed) and everything seemed fine. But the other day my mini 10v started with only a black screen. I then tried re-doing the drive replacement with a fresh install of SL, but - I don't know something happened -- at one point when I tried rebooting, I saw a GREEN GECKO which looked pretty ominious. I've since tried the drive replacement a few times and still get a black screen. I have also tried booting with a DOS USB flash drive, but get no response, just a black screen. While booting with the DOS USB flash drive, I've started up pressing f12, f2, 2, fn-B and fn-end, but get no response, just a black screen.
Any suggestions? Is all hope lost?