Hi,
I am getting the exact same error on a CentOS 6.2 X86_64 machine that I have just setup.
Removed and re-installed ALL the *virt* and *qemu* packages ( re-installed from the distro CD ).
The machine is a DELL Optiplex 755 with an Intel x86_64 processor.
I found there was a similar bug on Fedora a while ago and it was fixed here:
https://bugzilla.redhat.com/show_bug.cgi?id=726167
Not sure if the two are related but it seems likely given the descriptions...
Regards, D