"Headers already sent" warning interferes with login

While attempting to log into WordPress while running version 1.4.2 of WP News Stream as the active theme, I encounter the following errors:

In browser at wp-login.php:
ERROR: Cookies are blocked due to unexpected output. For help, please see this documentation or try the support forums.

From error logs:
PHP Warning: Cannot modify header information – headers already sent by (output started at /my/site/path/wp-content/themes/wp-news-stream/includes/breadcrumbs.php:9) in /my/site/path/wp-login.php on line 418

PHP Warning: Cannot modify header information – headers already sent by (output started at /my/site/path/wp-content/themes/wp-news-stream/includes/breadcrumbs.php:9) in /my/site/path/wp-login.php on line 431

Removing the two empty lines between the blocks of php in breadcrumbs.php (or making it one continuos block of php solves the issue for me.