Catchable fatal error

Hi,

I’m trying to import some posts from an old movable type export that somehow weren’t imported when I first moved to wordpress and I get this error message:

Catchable fatal error: Object of class WP_Error could not be converted to string in /home/rosapomar/aervilhacorderosa.com/wp-includes/wp-db.php on line 791

I’ve checked wp-db.php line 791:

function _real_escape( $string ) {
		if ( $this->dbh && $this->real_escape )
			return mysql_real_escape_string( $string, $this->dbh );
		else
			return addslashes( $string );
	}

Line 791 is:

return addslashes( $string )

Can someone help me?

Thanks!