Thanks Bryan, I nearly missed it otherwise:
http://www.the-digital-picture.com/N...aspx?News=2822

My only question to Canon is with this line:
"The firmware to address this phenomenon will be available for download in late August, 2012."

I hope they're talking about lens firmware (although they're probably not, seeing as the Big White firmware has to be done at a repair centre).
I've never had the problem on my 7D, but it's been fairly common on my EOS 3. Can I get a firmware for that please?