Need Wordpress Help

On my sites when I click on a category it does not show a list of posts under that catgeory. Just goes to the last post under that category and to see any others they have to keep clicking previous post. As there are over 50 categories its painful.

Is there a plugin or some fix to make a dropdown list of posts show up when someone clicks on a particlular category. Use Brian Gardners Revolution theme for this particular blog.

Apart from the XML sitemap I also use Really Simple Sitemap Plugin which does list all my posts chronologically on the sitemap page but not under the posts categories.

Would appreciate a Wordpress guru amongst you giving me a fix to this.

One other request. I read somewhere that you needed an extra particular plugin to make Related Posts Plugin work correctly. Could someone tell me what it is please?

Thanks and rep for help.
Bugs

Really need some help with this. Can someone help please?

can you send the address (URL) so that i can check it. I am a wordpress master

Here is a great plugin to handle groupings of posts:

The Custom Post Relationship plugin

http://wordpress.org/extend/plugins/custom-post-relationships/

im really comfused are you saying only 1 post shows up on the page? if so you can change that in settings