wp-settings.php and wpmu-settings.php error_log message

I am getting the following three errors repeatedly in the error_log file. It's just started happening since the upgrade to 2.8.4a, although I've had some weird glitches since 2.8.2. Sorry that this is terribly n00b of me, but I gotta start somewhere. I can see what the lines in the files the messages refer to, I'm just not sure what to do with this information. Thanks for the help!

PHP Warning: Cannot modify header information - headers already sent by (output started at /home/mark/public_html/wp-settings.php:305) in /home/mark/public_html/wpmu-settings.php on line 155

PHP Warning: include_once(/home/mark/public_html/wp-content/sunrise.php) [function.include-once]: failed to open stream: No such file or directory in /home/mark/public_html/wp-settings.php on line 305

PHP Warning: include_once() [function.include]: Failed opening '/home/mark/public_html/wp-content/sunrise.php' for inclusion (include_path='.:disappointed:usr/lib/php:disappointed:usr/local/lib/php') in /home/mark/public_html/wp-settings.php on line 305