Access Log after clicking on the Calendar link.
x.x.x.x - - [22/Nov/2011:12:32:44 -0800] "GET /calendar.html HTTP/1.1" 200 11534 "http://www.domain.com/calendar.html" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2"
Nothing in the error log except a couple of references to a image that that no longer exist (something that needs to be cleaned up in the template)
Joomla is writing out all of the links properly, for example the calendar link points to '/calendar.html' instead of 'index.php?option=com_gcalendar&view=gcalendar&Itemid=525#year=2011&month=11&day=22&view=month'
Apache is receiving a request for /calendar.html and returning 200 (OK), but it appears that the content of index.php or the "main page" is being sent...