this is a problem for iReboot!? When I said that it recognizes only Win8 I wuold say that in the little menu (opened by a right click on the icon in the status bar) there's only Win8 and not also Vista like option..Do you have "enable fast boot" set in the W8 power options ?
If so, you are not really rebooting W8 when you think you are, just hibernating and resuming it.
Delivering fast boot times in Windows 8 - Building Windows 8 - Site Home - MSDN Blogs
What!? Sorry but I don't know what is it..EFI system?