Operating System: Windows 8 pro and Windows 7 Ultimate (Dual Boot) as well as a laptop with Vista home premium installed
Other Security Software: None (Disabled Windows Defender before installing Avast 8 Free)
Graphics Drivers: NVidia
This problem only happened on my windows 8 installation. I also had gogle chrome set to install with it. I was forced to use system restore to restore my computer to the system restore point that avast created prior to installation. I installed avast again with google chrome, then changed the setting in the behavioral shield to uncheck the option to prevent unauthoried modifications, and clicked ok. I then tried to load google chrome in metro mode and it crashed even after restarting again.
Again i was forced to restore the PC, and this time i installed avast with google chrome and did a custom install, choosing not to install the behavioral shield at all. this completely solved my problems. Even when you disable that first option after install, avast blocks changes that are made before you disable it, so just refusing to install that shield all together is the best option i see at this point.
As an extra note, this was on a fresh install of windows 8 pro. on my other two windows versions, i had to disable the unauthorized modifications setting in order to allow windows to boot without a long black screen delay.