Description of problem:
"sendkey ctrl-alt-delete" don't work via VNC

Version-Release number of selected component (if applicable):
#rpm -qa | grep kvm
kvm-qemu-img-83-204.el5
kvm-debuginfo-83-204.el5
etherboot-roms-kvm-5.4.4-13.el5
kvm-tools-83-204.el5
kmod-kvm-83-204.el5
etherboot-zroms-kvm-5.4.4-13.el5
kvm-83-204.el5

#rpm -qa | grep vnc
vnc-server-4.1.2-14.el5_5.4
gtk-vnc-0.3.8-3.el5
vnc-4.1.2-14.el5_5.4
gtk-vnc-python-0.3.8-3.el5


How reproducible:


Steps to Reproduce:
1.Boot guest with -vnc :10 
#/usr/libexec/qemu-kvm -no-hpet -usbdevice tablet -rtc-td-hack -m 2G -smp 2 -drive file=/root/zhangjunyi/win2008-r2-virtio.qcow2,if=virtio,boot=on,werror=stop -drive file=/root/zhangjunyi/mnt/win2008/Windows_Server_2008_R2_GA_EN.iso,media=cdrom -fda /usr/share/virtio-win/virtio-drivers-1.0.0-45801-1.0.0.vfd -net nic,vlan=0,macaddr=22:11:22:45:66:83,model=virtio -net tap,vlan=0,script=/etc/qemu-ifup -uuid `uuidgen` -cpu qemu64,+sse2 -balloon none -boot d -monitor stdio -vnc :10 -notify all
2.connect to vnc
#vncviewer 10.66.91.91:10
3.Press F8->Send Crtl+Alt+Del
  
Actual results:
Send keyboard Crtl+Alt+Del.however,guest can not accept these key successful.

Expected results:
After Send Crtl+Alt+Del,guest accept it.

Additional info:

1. I also tried send key via qemu command,guest accept it.
(qemu) sendkey ctrl-alt-delete