Go to Appearance > Design Settings > Edit All Default Design Settings and underneath the “Templates” heading make sure that the BuddyPress context and the other contexts associated with BuddyPress are set to appropriate layouts. It sounds like you may have one or more of those contexts set to “Home Page Layout”.
While you are there check that all the contexts are set to appropriate layouts. The only context that should be set to “Home Page Layout” is the Home page context.
Also see the following topic regarding the layout for BuddyPress single member area not working:
http://para.llel.us/support/groups/mingle-wordpress/forum/topic/problems-with-subpages-and-custom-sidebar/