For those using a 1and1.com hosting package, try adding..
Options -MultiViews
to the top of the .htaccess file, and append the mod_rewrite stuff after it. I guess with their shared serving packages, the MultiViews just goes nutty (apparently it’s enabled, though), and needs to be turned off before using mod_rewrite. They actually document this behavior at http://faq.1and1.com/dedicated_servers/managed_server/3.html
I guess this means I’m in favor of dropping MultiViews, though not fervently.
