BuddyPress.org

“I recently used the plugin Enable Multi-Site to configure WordPress Multi-Site for my Buddypress install. “

Seriously – this is not recommended. I always recommend people set it up manually. the plugin only does 2 or 3 things for you – not the whole business and it doesn’t do any server checks that need a human eye.

‘If I try to navigate back to the main URL, I get nothing but a blank screen. Strange….”

No, not strange – it’s a common error called a white screen of death. It means you have some php messed up somewhere.

Can you get in to admin? Go in there, disable plugins. 90% chance something in there does not work with multisite.