Using Moodle 1.8.2+ (2007021520)
When editing a course calendar, the 'event view mode' changes unexpectedly when switching months.

To reproduce the behaviour, log on as a user who is a teacher in more than one course, where each courses contains course events in the current month (e.g. August). Enter one of the courses, and click on the month title in the calendar to enter Calendar editing mode. So far you should see only the courses for the current course. Now edit the following month (e.g. September). This causes the view mode to change to "All courses" automatically, so events from other courses suddenly appear in the calendars.

The problem is caused by a missing HTTP parameter in the URL of the link to other months. e.g.

http://server/moodle/calendar/view.php?view=month&cal_d=1&cal_m=9&cal_y=2007

should be

http://server/moodle/calendar/view.php?view=month&course=4&cal_d=1&cal_m=9&cal_y=2007

to specify the current course.