I can confirm this problem. It will strike after upgrading to WP 3.1 if your server is running Microsoft Internet Information Serverices version 6 (IIS6), which ships with the operating system Windows Server 2003. It is not an issue with IIS7
, which ships with Windows Server 2008.
Your admin area will be accessible through /wp-admin (to login), but your entire front end, as long as you are viewing front page, published posts/pages or archives, (draft previewing not included) will be severely affected. Your (visitors) browser will complain that the site is not redirecting properly, and will not show the page.
Solutions: Either install the plugin mentioned in the above post, or similar one containg the line
This line should also work if inserted into functions.php of your theme (in the global scope, outside the actual functions).
Or, delay the upgrade to WP 3.1 until WP 3.1.1 is released.
The bug is (reported by me and) listed on WP Core Trac as being a critical bug to be fixed in 3.1.1. WordPress still supports IIS6 as web server platform, core developer/committer Nacin says.
Some users have complained that they cannot install the plugin, since they cannot log in. If you cannot log in using a direct URL to the admin area, then there are something else going on, too. The /wp-admin path should redirect you properly to the login page, if this canonical redirect bug is the only issue.