Possibble to install Buddypress on a sub-blog only?

Hi, 2 questions :

1. I wanted to know if it’s possible to activate BuddyPress on a sub-blog only.

2. Actually this is not my biggest problem. My problem is that the links in the toolbar of buddypress (as well as the one created in my sub-blog menu) are always pointing to my main site, on some pages like “members” which doesn’t exist.. actually not on my main blog. Logically, it would supposed to be linking in mysite.com/subsite/members … but now it’s linking to mysite.com/members.

I’m currently running my multi-site on WordPress 3.0.1.

Thanks in advance for your help, Alex.