I am bit confused now

Maybe I did not explain the problem properly. For example there is an event that belongs to the 'Mass Media' category and it works fine. When I edit this event the 'Mass Media' checkbox is not checked and if I save it like that the event won't belong to any category now.

So, when the event edit form is loaded the category checkboxes are not initialized.

Is this the issue you knew about?

Marius