Strangely enough, I ran into this same problem today when we moved to a new server. It wasn't happening only on past events, but when we showed future events (we have almost 9000).
No php error was being displayed in the logs or with WP_DEBUG turned on. After a lot of debugging, it turned out the script was running out of memory.
thorwik: EDIT: I will post the fix I came up with and put a link to it here sometime tomorrow.
Marcus, we've had out of memory errors on all the listing pages because they pull all of the events from the database, when only 20 need to be shown on the page. I've had to rewrite both the admin listing function and all the events listings pages, to pass limit and offset to $args to get the events, and then remove those to get EM_Events::count(), which works much better. Any chance of this being refactored into a future release? I've searched around and noticed I'm not the only one who's been running into out of memory issues with the plugin. :)