Rewrite Rule problems

Using “/archives/%year%/%monthnum%/%day%/%postname%/” as my customised permalink.
The permalink manager gave me a bunch of rewrite rules to add to my .htaccess.
These include:
RewriteRule ^archives/([0-9]{4})?/?([0-9]{1,2})?/?([_0-9a-z-]+)?/? ([0-9]+)?/?$ /index.php?year=$1&monthnum=$2&name=$3&page=$4 [QSA]
RewriteRule ^archives/([0-9]{4})/([0-9]{1,2})/([_0-9a-z-]+)/ (feed|rdf|rss|rss2|atom)/?$ /wp-feed.php?year=$1&monthnum=$2&name=$3&feed=$4 [QSA]
RewriteRule ^archives/([0-9]{4})/([0-9]{1,2})/([_0-9a-z-]+)/ trackback/?$ /wp-trackback.php?year=$1&monthnum=$2&name=$3 [QSA]
However…
If I have any of these 3 uncommented in my .htaccess, I get internal server error.
No idea why, as I am a complete newbie when it comes to mod_Rewrite related stuffage.
Any help on this would be great, thanks.