Applied Dan's fix for the incorrectly named Sha1 class.
diff --git a/system/libraries/Sha1.php b/system/libraries/Sha1.php
index 05a4234..1a65757 100644
--- a/system/libraries/Sha1.php
+++ b/system/libraries/Sha1.php
@@ -42,7 +42,7 @@
  * @author		ExpressionEngine Dev Team
  * @link		http://codeigniter.com/user_guide/general/encryption.html
  */
-class CI_SHA {
+class CI_SHA1 {
 
 	public function __construct()
 	{