Fatal error - class-wp-filesystem-direct.php on line 68

No such file can be located..

Perhaps coincidence..
Loaded WMPMU and a few of WMPU plugins - working on events.. attempted update for enews = get this debug error...

Fatal error: Call to undefined function reset_mbstring_encoding() in /home/site/public_html/wp-admin/includes/class-wp-filesystem-direct.php on line 68

Can find no such file..