Warning: Cannot modify header information - headers already sent by - classic

Hi folks, I'm running some code locally which should produce this fun error we all know and love: Warning: Cannot modify header information - headers already sent by... but does not. Switching from 5.3 to 5.2 reveals the error and running it on another server with 5.2 also shows the error. I don't believe the version has anything to do with it, but who knows. I set error_reporting = E_ALL | E_STRICT and verified that display_errors = On, still nothing. Any ideas what could be allowing a header('Location:'); call to redirect without throwing an error after output has been sent to the browser? Marc