This error is due to a Device Driver that is unsigned. On a Windows 8.1 load failure, it will start up in repair mode. Select Advanced Repair, then select Change Startup Options and press Restart. The system will then provide a menu of startup options. Select Disable Device Signature Verification (Option 7). This will then allow you to boot into Windows 8.1 to remove the offending device.
To determine which device is causing the issue, use the SigVerif.exe program.
In my case, the program was due to an Intel Wireless/Bluetooth driver, which I promptly uninstalled and allowed Windows Update to install a new version.