现象：注销/切换用户后黑屏，不出现用户选择界面

解决方法：

可能是由于应用服务或者启动项不能正确结束导致注销/切换用户的操作不能及时完成。以“clean boot”形式启动系统，除了Windows系统服务外，禁用所有应用服务和启动项，用二分法逐步缩小范围、最终确定引发问题的服务或启动项，禁用之

参考帖子 http://www.sevenforums.com/general-discussion/20242-monitor-goes-black-when-attempting-switch-user.html

1. Boot in safe mode, see if you can switch users without trouble (you 95% will be able to)
2. If safe mode user switching works, then you have a problem with a third party service.
3. Follow these steps to perform a clean boot and isolate some of the processes that might be troublesome

关于“clean boot”参考 http://support.microsoft.com/kb/929135

（btw，我的系统中是 vmware authorization service、vmware usb arbitration service、vmware workstation server 这3个服务导致黑屏问题的发生）