I'm currently running the latest Virtualbox (4.3.6) with a full copy of Windows 8 (32-bit).
I installed OCTGN and everything went without a hitch, and the updater/loader window thing (the one with the "The Spoils" ad on it) ran fine, and then OCTGN opened as usual, except the screen within the window was totally black. The underlying UI was still active, as my mouse changed to the appropriate things in the appropriate spots and I was even able to close it with the regular "X" button, but you couldn't see anything.
Does anybody know anything about this issue in Vbox or Windows 8? Or a solution? I tried reinstalling OCTGN and rebooting the computer (in both orders), and it didn't do anything.
Try turning Hardware Acceleration off. There is a setting for it in the octgn config folder settings file(it's .json I believe)