Index: wp-admin/includes/class-wp-ms-themes-list-table.php
===================================================================
--- wp-admin/includes/class-wp-ms-themes-list-table.php	(revision 16619)
+++ wp-admin/includes/class-wp-ms-themes-list-table.php	(working copy)
@@ -97,7 +97,7 @@
 			}
 		}
 
-		if ( !current_user_can( 'update_themes' ) )
+		if ( !current_user_can( 'update_themes' ) || $this->is_site_themes )
 			$themes['upgrade'] = array();
 
 		if ( $s ) {
@@ -235,7 +235,7 @@
 			$actions['enable-selected'] = __( 'Enable' );
 		if ( 'disabled' != $status )
 			$actions['disable-selected'] = __( 'Disable' );
-		if ( current_user_can( 'update_themes' ) )
+		if ( current_user_can( 'update_themes' ) && !$this->is_site_themes )
 			$actions['update-selected'] = __( 'Update' );
 
 		return $actions;
@@ -344,6 +344,8 @@
 
 		echo "</tr>";
 
+		if ( $this->is_site_themes )
+			remove_action( "after_theme_row_$theme_key", 'wp_theme_update_row' );
 		do_action( 'after_theme_row', $theme_key, $theme, $status );
 		do_action( "after_theme_row_$theme_key", $theme_key, $theme, $status );
 	}