That is a strange priority setting (-1000??? huh???) for the Grid Video Player, but I do not think that plugin is causing the problem.
http://codex.wordpress.org/Function_Reference/add_filter
/home/rafael/public_html/wp-content/plugins/gridvideoplayer/gvpscriprts.php, line 482 add_filter('pre_set_site_transient_update_plugins', 'mplayer_check_for_plugin_update', -1000);