I've had a few posts about this, I guess i should have been more specific.
but my .htaccess is currently this;

RewriteEngine On
RewriteRule ^article/(.*)/(.*) article.php?$1=$2
RewriteRule ^index/(.*)/(.*) index.php?$1=$2

I wanted it to do subcategories like
http://ap-gfx.com/index/category/php/subcategory/tips

So I changed my .htaccess to this;

RewriteEngine On
RewriteRule ^article/(.*)/(.*) article.php?$1=$2
RewriteRule ^index/(.*)/(.*)/(.*)/(.*) index.php?$1=$2&$3=$4

Is this right and my server is acting up or is the code wrong.

Add this one
RewriteRule ^index/(.*)/(.*) index.php?$1=$2
to keep handling urls like /index/category/catname