as per topic, my calender widget is showing the entries from the synced N900 calendar, the synced Mail for Exchange calendar, but it never shows any entries for the nonsynced SmartBirthdays calendar. these are the only 3 calendars marked as visible and their contents show in the calendar app, but the widget doesnt show birthdays

does anyone know why?

Two ideas

When you go to Settings in the Calendar Application, is the "Birthdays" Calendar there? If not go to "New" and add the smart Birthday calendar.

Secondly, if you already have done the above and it still doesnt work - delete (yes delete) the calendar and re-create it. This usually resyncs and solves this problem.
Deleting the calendar wont delete individual birthdays but only delete the entries from the calendar.