Missing pomo/mo.php error in 2.9.1

heylo!

i updated my WordPress automatically from 2.9.0 to 2.9.1
last week and everything seemed to be fine for a few days.
last thurs i updated the content on one my pages. again,
everything was fine and i went to sleep. on friday, i woke up
and found this message when accessing the site.
—

Warning: main(/home/content/s/i/r/sirdemon/html/wp-includes/pomo/mo.php): failed to open stream: No such file or directory in /home/content/s/i/r/sirdemon/html/wp-settings.php on line 342

Warning: main(): Failed opening ‘/home/content/s/i/r/sirdemon/html/wp-includes/pomo/mo.php’ for inclusion (include_path=’.:/usr/local/lib/php’) in /home/content/s/i/r/sirdemon/html/wp-settings.php on line 342

Fatal error: Cannot instantiate non-existent class: noop_translations in /home/content/s/i/r/sirdemon/html/wp-includes/l10n.php on line 437

—

any ideas?
thanx!
sir demon brown