Index: wp-admin/includes/plugin.php
===================================================================
--- wp-admin/includes/plugin.php	(revision 17454)
+++ wp-admin/includes/plugin.php	(working copy)
@@ -563,7 +563,7 @@
 function deactivate_plugins( $plugins, $silent = false ) {
 	if ( is_multisite() )
 		$network_current = get_site_option( 'active_sitewide_plugins', array() );
-	$current = get_option( 'active_plugins', array() );
+	$current = (array) get_option( 'active_plugins', array() );
 	$do_blog = $do_network = false;
 
 	foreach ( (array) $plugins as $plugin ) {
@@ -583,7 +583,7 @@
 			$key = array_search( $plugin, $current );
 			if ( false !== $key ) {
 				$do_blog = true;
-				array_splice( $current, $key, 1 );
+				unset( $current[ $key ] );
 			}
 		}