Index: wp-admin/includes/class-wp-plugins-list-table.php
===================================================================
--- wp-admin/includes/class-wp-plugins-list-table.php	(revision 17031)
+++ wp-admin/includes/class-wp-plugins-list-table.php	(working copy)
@@ -362,7 +362,7 @@
 				} else {
 					if ( current_user_can( 'manage_network_plugins' ) )
 						$actions['network_activate'] = '<a href="' . wp_nonce_url('plugins.php?action=activate&amp;networkwide=1&amp;plugin=' . $plugin_file . '&amp;plugin_status=' . $context . '&amp;paged=' . $page . '&amp;s=' . $s, 'activate-plugin_' . $plugin_file) . '" title="' . __('Activate this plugin for all sites in this network') . '" class="edit">' . __('Network Activate') . '</a>';
-					if ( current_user_can('delete_plugins') )
+					if ( current_user_can( 'delete_plugins' ) && ! is_plugin_active( $plugin_file ) )
 						$actions['delete'] = '<a href="' . wp_nonce_url('plugins.php?action=delete-selected&amp;checked[]=' . $plugin_file . '&amp;plugin_status=' . $context . '&amp;paged=' . $page . '&amp;s=' . $s, 'bulk-plugins') . '" title="' . __('Delete this plugin') . '" class="delete">' . __('Delete') . '</a>';
 				}
 			} else {
Index: wp-admin/plugins.php
===================================================================
--- wp-admin/plugins.php	(revision 17031)
+++ wp-admin/plugins.php	(working copy)
@@ -195,12 +195,17 @@
 
 			//$_POST = from the plugin form; $_GET = from the FTP details screen.
 			$plugins = isset( $_REQUEST['checked'] ) ? (array) $_REQUEST['checked'] : array();
-			$plugins = array_filter($plugins, 'is_plugin_inactive'); // Do not allow to delete Activated plugins.
-			if ( empty($plugins) ) {
+			if ( empty( $plugins ) ) {
 				wp_redirect( self_admin_url("plugins.php?plugin_status=$status&paged=$page&s=$s") );
 				exit;
 			}
-
+			
+			$plugins = array_filter($plugins, 'is_plugin_inactive'); // Do not allow to delete Activated plugins.
+			if ( empty( $plugins ) ) {
+				wp_redirect( self_admin_url( "plugins.php?error=true&main=true&plugin_status=$status&paged=$page&s=$s" ) );
+				exit;
+			}
+						
 			include(ABSPATH . 'wp-admin/update.php');
 
 			$parent_file = 'plugins.php';
@@ -330,14 +335,16 @@
 
 <?php if ( isset($_GET['error']) ) :
 
-	if ( isset($_GET['charsout']) )
+	if ( isset( $_GET['main'] ) )
+		$errmsg = __( 'You can not delete a plugin that is active on the main site. Please deactivate the plugin from the site admin and try again.' );		
+	elseif ( isset($_GET['charsout']) )
 		$errmsg = sprintf(__('The plugin generated %d characters of <strong>unexpected output</strong> during activation.  If you notice &#8220;headers already sent&#8221; messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.'), $_GET['charsout']);
 	else
 		$errmsg = __('Plugin could not be activated because it triggered a <strong>fatal error</strong>.');
 	?>
 	<div id="message" class="updated"><p><?php echo $errmsg; ?></p>
 	<?php
-		if ( !isset($_GET['charsout']) && wp_verify_nonce($_GET['_error_nonce'], 'plugin-activation-error_' . $plugin) ) { ?>
+		if ( !isset( $_GET['main'] ) && !isset($_GET['charsout']) && wp_verify_nonce($_GET['_error_nonce'], 'plugin-activation-error_' . $plugin) ) { ?>
 	<iframe style="border:0" width="100%" height="70px" src="<?php echo 'plugins.php?action=error_scrape&amp;plugin=' . esc_attr($plugin) . '&amp;_wpnonce=' . esc_attr($_GET['_error_nonce']); ?>"></iframe>
 	<?php
 		}