Prevent from leaving unsaved "New Issue" page.
After leaving a partial filled "New Issue" page by accident, the "Description" text field as well as the combo boxes are restored to there defaults (=> empty). I remember that MoinMoin was presenting a warning box in this case and Bugzilla was able to restore all the fields. This is true with Firefox, Bugzilla, MoinMoin versions which were up-to-date two years ago so it should basically possible to find a solution for the very annoying issue.
Using Firefox 3.6.