enotalone - 10:37 pm on Jan 18, 2012 (gmt 0)
Thanks tedster, g1smd. I did not have a canonical tag and the forum main page is indexed both as domain.com/forum/ and domain.com/forum/index.php. I applied the canonical tag and 301 redirect to the index.php version. I went through the website many times in hope of finding a technical error that would cause this miscalculation but so far found nothing.