buddypress default theme not working on all blogs

Hi.. I’m having a problem with the default buddypress working on all my blogs. The main site displays the theme perfectly as it does on 2 other sites I installed it on. The problem I am having is on a multi-site install. The front page or main page of my site is what I want the subdomains to look like (default buddypress theme) what the subdomain blogs are showing is the Twenty Eleven theme. I have no idea what went wrong or how to fix this.

I’m very close to getting this to work and it’s really important to me that I get it figured out. I’ve just discovered your software 2 days ago and I’ve been enjoying learning how to use it, but I’ve hit a brick wall.

any help will be appreciated.. just please keep it simple for me, step by step please.. ??

thank you very much in advance.. ??