This bug has been copied from bug #545737 and has been proposed to be backported to 5.5 z-stream (EUS).
Since virtio-win in RHEL 5 is a package in the Supplementary channel, there is no Z-Stream for it. There is no need to clone bugs from 5.6 to 5.y.z, when the package it released it will be available to all users of RHEL 5, regardless of minor release.