This is fixed upstream, should be backported into RHEL 5
This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
After careful review (I looked at the 400+ changes between RHEL6 and upstream, then the 450+ changes between RHEL5 and RHEL6 kvm), I don't think this bug is even present on RHEL5. The AMD initial TSC fixes, which are the most important and clear bugfixes, have been backported into RHEL5 already, and the upstream changes which caused this bug to present have not been incorporated into the RHEL5 codebase. I think the only thing we need to do here to close the bug is to simply test run an F14 guest with 2 VCPUs on an AMD processor to make sure it boots.
This clone of the bug can be closed; it's in POST for 6.1, but I don't believe RHEL5 ever caught this particular bug.