Permalink Fix & Disable Canonical Redirects Pack plugin by Chris Cheney, Nick Schalk and Mark Jaquith ensures the REQUEST_URI variable is set during the initialization of WordPress, allowing permalinks to work correctly. The REQUEST_URI variable is not set correctly by the server platform. This plugin builds each variation of REQUEST_URI by peicing together other available variables.
Download and info: http://wordpress.org/extend/plugins/permalink-fix-disable-canonical-redirects-pack/