Index: branches/RC/core/units/general/helpers/filenames_helper.php
===================================================================
diff -u -r8929 -r10098
--- branches/RC/core/units/general/helpers/filenames_helper.php	(.../filenames_helper.php)	(revision 8929)
+++ branches/RC/core/units/general/helpers/filenames_helper.php	(.../filenames_helper.php)	(revision 10098)
@@ -77,8 +77,8 @@
 							)
 						)
 			{
-				if (substr($append, -1) == 'z') $append .= 'a';
-				$append = substr($append, 0, strlen($append) - 1) . chr( ord( substr($append, -1) ) + 1 );
+				if (mb_substr($append, -1) == 'z') $append .= 'a';
+				$append = mb_substr($append, 0, mb_strlen($append) - 1) . chr( ord( mb_substr($append, -1) ) + 1 );
 			}
 
 			return $filename.$append;