Permalinks Problem

Hi chaps. Got an odd one here. If I switch permalinks off my .htaccess looks like:

208-122-30-113:/var/www/pbgs.org# cat .htaccess
# BEGIN WordPress

# END WordPress

If I switch it onto any other option it looks like this:

208-122-30-113:/var/www/pbgs.org# cat .htaccess
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

The problem is if I use any other option other than ‘off’ I end up with a non working site giving me 404 for all pages apart from home. mod_rewrite is installed and enabled so I’m at a bit of loss here.

Any ideas all?