I did a fresh installation of Windows 8 64 bit, build 9200 (released on aug 16th). I installed the drivers and some basic softwares like NetBeans, mingw, iis server and php. For the first few times, it was restarting normally. But then at shutdown, it would show the shutdown screen for some seconds and then turn black for about 4 mins (similar to what happens at hibernation). I disabled the "fast startup" option in power options, but the problem still persists. Windows 7 and Ubuntu shut down normally. specs: 4gb ram, 750 gb sata hdd,
solved by installing Windows Updates released during October. It was a serious bug in the OS, afaik. Now even hibernate takes upto 30 secs max. Still, win 8 is too buggy for release.