Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 15506)
+++ wp-includes/functions.php	(working copy)
@@ -86,7 +86,7 @@
 	global $wp_locale;
 	$i = $unixtimestamp;
 	// Sanity check for PHP 5.1.0-
-	if ( false === $i || intval($i) < 0 ) {
+	if ( false === $i || ( intval($i) < 0 && -1 === strtotime( '1969-01-01' ) ) ) { 
 		if ( ! $gmt )
 			$i = current_time( 'timestamp' );
 		else