Just upgraded to 3.0.4 and…Fatal error?

I get this error:

Fatal error: Cannot redeclare is_rtl() (previously declared in /homepages/45/d94430377/htdocs/yodel/wp-includes/locale.php:347) in /homepages/45/d94430377/htdocs/yodel/wp-includes/locale.php on line 349

The local.php scrap of code (lines 346-349) in question:

function is_rtl() {
global $wp_locale;
return $wp_locale->is_rtl();
}

This page was replaced or revised with the update. Anybody got a clue as to what went wrong here?

Thanks for any help you can give.

Max