the '/' is needed for some servers

plugins/owncloud/owncloud.php

@@ -1,7 +1,7 @@
 <?php
 // This plugin creates ReadLater bookmarks in your owncloud.
 // The plugin needs a 
-// define('OWNCLOUD_URL','http(s)://your.serv.er/owncloud'); 
+// define('OWNCLOUD_URL','http(s)://your.serv.er/owncloud/'); 
 // in your config.php. The parameter is actually global. user_pref
 // with editable parameter in future versions.