Loading xml via php

i just had flash loading some cross domain xml via php’s readfile, then, it stopped working and now i get this PHP error:

Warning: readfile(http://xml.weather.yahoo.com/forecastrss?p=USPA0260) [function.readfile]: failed to open stream: HTTP request failed! HTTP/1.1 999 Unable to process request at this time -- error 999 in E:\WWW Root\myDomain.com\weather.php on line 6

any ideas?