Recently we had faced a unique solution with regards to Page Rank .In the index page for a particular site,we faced this situation:

example.com/: PR 4
example.com/index.php :PR 3

Though index.php is the default file for the site ,wherever the inner pages were linked to the home
page,we had given the following URL example.com/index.php.

Hence we noticed the split in page rank.

The solution was provided by the Moderator in the forum forums.seo.com:
1.Change all the inner page links to point to "/"
2.Use an htaccess directive to redirect your link weight from "index.php" to "/"

Check this forum forums.seo.com/showthread.php?t=4591 for reading through the entire posting and the replies.