Windows 8 machine BSOD at boot with message ATTEMPTED EXECUTE OF NOEXECUTE MEMORY. Windows recovery tools could not fix. Rebuilt BCD for UEFI machines and was able to boot into safe mode but no regular boot. )xc0000001 error message but safe mode worked. Checked for recently installed Windows updates and programs. Avast Internet Security updated two days before the BSOD so I didn’t suspect it. After many hours I realized that the machine was probably never rebooted after AIS updated. Uninstalled AIS and my machine is back! Not sure but the problem might be related to the rootkit protection in AIS. Seemed like there was a straightjacket on the boot settings. Not really sure that rootkit protection is necessary on UEFI.