Upgraded to Windows 8.1 on the 19th of October.
Experience the bridged network adapter issue, so uninstalled my old version 4.2 of VirtualBox and installed version 4.3. This allowed me to bridge the network cards again. However, the host machine now fails (BSOD) with a CRITICAL_STRUCTURE_CORRUPTION error.
I am about to begin a series of diagnostic steps to see if I can get some stability back in the platform, as going back to Windows 8 does not appear to be an option.
I am trying two things initially 1) Run the VMs with NAT only, and 2) Reinstall earlier version of VB.
Will let you know how things track. Hopefully this will help with root cause analysis.
Update: Changing to NAT only had no effect - failed with the same error after 27 mins. I will try setting # of CPUs to 1 as recently suggested, before I downgrade VB.
Update 2: Likewise, have reduced the number of CPUs to 1 and it has been running for over and hour now