(bad form replying to myself)
I've found the issue upstream:
https://bugzilla.redhat.com/show_bug.cgi?id=729586
Last comment there saying there are patches in an as yet unreleased kernel-2.6.32-229.el6. I've had a quick look at the SRPMS upstream and don't see that one yet so a related question: how quickly do they release these or make them available for testing?
Cheers,
Steph