Warning: timezone_open() [function.timezone-open]: Unknown or bad timezone (UTC-4)

WPMU 2.9.1.

After update I got Timezone for all our blogs set up as Abidjan? I tried to change to our country timezone on of the blog and I go the following error.

Warning: timezone_open() [function.timezone-open]: Unknown or bad timezone (UTC-4) in /home/track/public_html/wp-includes/functions.php on line 3424

How can I fix it?