If you've just downloaded the Windows 8 Release Preview ISO using Google Chrome - don't.

Redo it, using IE.

I actually downloaded the image, didn't checksum the ISO (i.e. check it was a 100% copy of the one off the Microsoft site), hooked the ISO up to VirtualBox and got this:

"No Device drivers were found. Make sure that the installation media contains the correct drivers, and then click OK."

I tried a multitude of solutions, but the only way was: download the ISO through IE.

Here you'll find other stuff on how to solve problems while installing Windows 8 on VirtualBox.

Bonus: tips and tricks for Windows 8.

edit, 2012-08-16:

Having used Chromium (i.e. Chrome in developer's edition) to download the Windows 8 RTM, there were no problems with the above.