My setup is as follows:
Host OS: Debian Wheezy amd64 stock kernel (3.2), virt-manager v0.9.1
Guest VMs: A bunch of Linux based servers - CentOS 6, Debian 6/7, Ubuntu 12.04 (all amd64 with stock kernel). All of them defined using virt-manager GUI interface.
From the virt-manager, I am able to shutdown/reboot the Debian and Ubuntu guest OSs but not the CentOS 6 guests.
For the CentOS 6 guests, I have to resort to "Force off"
I have looked at the syslog and messages log files but do see anything to correlate between host and guest OS.