CGI Error while using header() to redirect

it says the cgi application misbehaved by not returning a complete set of http headers. my code is pretty simple: just: ob_start(); [some html stuff here] header("Location: http://www.domain.com"); exit; ob_end_flush(); what puzzles me is that sometimes it will not give me the above error and work perfectly. a refresh on the error page will send me to the redirected url. i am running on php4.22, win2k server sp3. any thoughts on why this error is so? --b.c. lance