Only 20 first instances shown

Drupal version 6.20

I'm creating a node view to act as an event list for my website. I want to show the upcoming events in a table format with 10 events / page with ajax pager. If I set the "Items per page" to anything else that 0 (unlimited) I get only the first 20 events from the database. (i.e. if I set it to 2 then I get ten pages with two event on a page and with 10 I get two pages but with 0 = unlimited it returns all 25 events)

Any ideas how to fix this?