I upgraded a Windows 8 machine running Virtualbox 4.3.0 to Windows 8.1 (released today). The Windows 8.1 machine is acting as a host OS to 64bit Linux running as the guest. After the upgrade the host OS crashes every few minutes with a CRITICAL_STRUCTURE_CORRUPTION error and reboots. I collected 5 minidumps which I have uploaded to https://www.dropbox.com/s/5pm12sbe0fu8evb/minidumps.zip
I wonder if the Virtualbox drivers are experiencing compatibility issues with the now released Windows 8.1.