I've found that Events Manager conflicts with Widget Entries.
@row 26 of events-manager/em-events.php there's
$content = apply_filters('em_content_pre', '', $page_content);
I understand that's needed as an hook to "Create Custom Event Information Pages" (http://wp-events-plugin.com/tutorials/create-custom-event-information-pages/) but looking at Codex http://codex.wordpress.org/Function_Reference/apply_filters seems that the code should be simply
$content = apply_filters('em_content_pre', $page_content);
as the 'em_content_pre' filter may be applied to the string passed with the second parameter, beeing the third just an optional value.
There's any special reason you're passing an empty string as second parameter? That seems weird....