Index: wp-includes/plugin.php
===================================================================
--- wp-includes/plugin.php	(revision 5760)
+++ wp-includes/plugin.php	(working copy)
@@ -237,8 +237,9 @@
  * @return string The name of a plugin.
  */
 function plugin_basename($file) {
-	$file = preg_replace('|\\\\+|', '\\\\', $file);
-	$file = preg_replace('/^.*wp-content[\\\\\/]plugins[\\\\\/]/', '', $file);
+	$file = str_replace('\\','/',$file); // sanitize for Win32 installs
+	$file = preg_replace('|/+|','/', $file); // remove any duplicate slash
+	$file = preg_replace('|^.*/wp-content/plugins/|','',$file); // get relative path from plugins dir
 	return $file;
 }