Este é um problema conhecido no Windows 8 de 64 bits e no Windows Server 2012
Fonte: Seu Windows 8 não será reiniciado se suas seções do Registro forem maiores que 2 GB. Por quê?
The Windows Registry is a directory which stores settings and options for the operating system for Microsoft Windows. It contains information and settings for all the hardware, operating system software, most non-operating system software, users, preferences of the PC, and so on. A Registry Hive is a logical group of keys, subkeys, and values in the registry that has a set of supporting files containing backups of its data and are located in the \system32\, \winnt\, etc locations.
If you are running 64-bit Windows 8 or Windows Server 2012, and the size of your Windows Registry Hives are larger than 2 GB in size, your computer just will not restart.
This is because the registry hives in x64-based version of Windows have a 2 GB size limit, and if the size exceeds this limit, the system is unable to restart.
Microsoft has confirmed that this is a problem and a known issue.
If you are experiencing this particular issue, then you can download Hotfix 496812 via KB2978366