The following solved it:
# paxctl-ng -m /usr/bin/qemu-system-x86_64
After that I can run and interact with VMs normally.
That helped me too. Thank you!
But I found a better way fixing it, it's in RH faq:
http://www.linux-kvm.org/page/FAQ#When_I_click_the_guest_operating_system_window.2C ...