If you find that you are receiving errors within your event log from ILO and your server is a HP, check out the link below. There is a known issue with ILO 2 Management Controller driver on a few HP servers which can cause a shutdown or restart request to halt.
HP ProLiant iLO 2 Management Controller Driver Version 18.104.22.168 released in ProLiant Support Pack (PSP) Version 8.20 may prevent Microsoft Windows Server 2003 or Microsoft Windows Server 2008 from completing a shutdown or restart request. The shutdown or restart requests may halt at the final stages of shutdown even though other system components (such as the mouse) are still responsive.
More details can be found at: http://tinyurl.com/lcar22