Stage environment for Magento for dummies - 500 internal server error

Question

I'm brand new to server side setup and creating staging environments. I have a magento live environment I've setup, but now I want to setup a stage environment (stage.mystore.com) and practice rolling from stage to live. But, I'm a newb to this and having issues.

I started by following this tutorial to the T, but am currently stuck:

http://www.crucialwebhost.com/kb/setting-up-a-magento-staging-area/

I can load my homepage on the stage subdomain, but any link I click on gives me an "500 internal server error". Secure and unsecure.

I've read around a lot, and it seems like I probably need to either edit something else in my .htaccess or core_config_data but I'm uncertain what to do next.

Can anyone provide more complete step by step instructions for this last part for me?

Answer 1

PhilB's response worked. I just needed to do that change to the varien.php file AND clear out all cookies from my live server in my browser and then I could login. thanks.