Paul Randal (8/14/2009)
Ok - this has now been proven to be a bug inside MS, with a simple repro. Alex - let me know if you want to push for a hotfix for this and I'll give you the internal bug number that's been opened that you can use when you call PSS (and some high-level names to add to make sure you get the correct response).
Thanks for your help. I'm away now for a few weeks. I've left all the details (including your message above) with my colleagues, and they may take you up on this offer. Failing that, I'll get onto it upon my return.
Thanks for your help here, it's been great!