Warning: require(./wp-blog-header.php) [function.require]: failed to open stream

Hi,

I have multiple sites; all of them work, except for this one:
davidfranklin.net/dareoftheday

When I go to that site, I get this message:
Warning: require(./wp-blog-header.php) [function.require]: failed to open stream: No such file or directory in /home/content/u/p/o/uposatha/html/dareoftheday/index.php on line 17

Fatal error: require() [function.require]: Failed opening required ‘./wp-blog-header.php’ (include_path=’.:/usr/local/php5/lib/php’) in /home/content/u/p/o/uposatha/html/dareoftheday/index.php on line 17

The strange thing is that I only get this message when going to the root address; if I go to an individual post under that directory, e.g. http://davidfranklin.net/dareoftheday/make-the-choice/, I don’t get an error message.

Thanks in advance!