1- I will use the filter events by category, it works also great!
2- No error when selecting some categories in the filter events by category box, as an improvement the user shouldn't have the possiblity to check this box when no category is selected, or the user will not get an error and can add events with no category selected.
3- The problem is caused because IE convert special character in url to UTF-8 (hex), and that caused a problem with javascript function, and the modal window shows the first parent page after the page with special character, exemple in my site:
dnnModal.show('
http://mysite.no/Forside/Felles-tjene...',/*showReturn*/false,550,950,true,'')
I solved the problem by replacing special characters by normal charaters in the url (%C3%B8 and %C3%A5)
4- As you recommended, i solved the problem by deleting all events, changing and resetting the Event TimeZone, and recycling application demain.
Thanks Roger,