Perhaps you should look at this,

http://googlewebmastercentral.blogspot.com and the section "Crawling and indexing your multilingual website" which tells you how to get the site crawled in several languages.

Thanks for the link

To make all of your site's content more crawlable, avoid automatic redirections based on the user's perceived language. These redirections could prevent users (and search engines) from viewing all the versions of your site. And last but not least, keep the content for each language on separate URLs - don't use cookies to show translated versions.
Source: http://googlewebmastercentral.blogspot.com

Looks like they have the same idea I was thinking of, but they're using mod_rewrite.