After an upgrade to WordPress 3.1, everytime I hit the front page of my wordpress site I was getting 100% CPU and the page would fail to render, no 404 just a hourglass and lots of waiting. However I could get to the admin site fine.
It turned out to be a problem that is discussed here: http://wordpress.org/support/topic/windows-server-infinite-redirect-after-upgrading-to-31?replies=4#post-1958450
The fix/workaround for now is to do the following: Open the blog’s admin dashboard (thankfully this is still functional) and install the Permalink Fix & Disable Canonical Redirects Pack plugin and all is back to normal again.
For more info see these links:
http://wordpress.org/extend/plugins/permalink-fix-disable-canonical-redirects-pack
http://www.boche.net/blog/index.php/2011/02/27/wordpress-3-1-upgrade-issues/