mod_rewrite + SEO

[redbullmarky]

Hi all
I've recently added some mod_rewrites to a htaccess file, turned of transparent session ID's, etc, with the aim of helping my pagerank and just to keep things alot tidier.

here's one of them:
RewriteRule ^news(/[0-9]*/[0-9]*)?/article([0-9]*).htm(l)?$ news/article.php?id=$2 [L]

which basically allows things like: article345.htm -> article.php?id=345

now - all my articles have already been picked up by MSN Search and are starting to get crawled by google. how can i make sure that all these old pages are replaced in Google and MSN, etc with the new, user-friendly article names?
i tried this:
RewriteRule ^news/article.php?id=([0-9]*)$ news/article$1.htm [r=301, L]

but i get 500 internal server errors.
Anyone know what i can do?

Cheers
Mark