Unnecessary "Leave Site" confirmation dialogs


TS Evangelist
I've noticed somewhat recently that Gmail will frequently show the "Are you sure you want to leave this site?" dialog box when navigating away -- often with no logical or discernible reason. In many cases it appears when loading Gmail, then clicking on just a single email, then trying to navigate away from the site.
Every time I try to leave gmail, it asks me if I am sure. Of course I am sure. Any body know why??