I have the exact same error with the latest release of buddypress and wp 2.7, and just as jfcarter explained my templates are also in the correct directories with the correct permissions. The system looks for “buddypress-home” instead of “member-themes”
wp-content/member-themes/buddypress-home/index.php) [function.load-template]: failed to open stream: No such file or directory in /wp-includes/theme.php on line 822
