OK this has officially driven me nuts this week.
I've posted it as a bug on the Pro Tools Ideascale.
Please feel free to vote on it here:
http://protools.ideascale.com/a/dtd/...ug-/29438-3779
I know only 3 in 100 reports actually turn out to be bugs but this one is weird! I've tried for the life of me to track this down as operator error...