Re: The page you were looking for was not found.
Mine is doing something similar, I think.
WPMU was installed first… worked fine, tested some blogs and users.
Installed BP via the Plugins installer… activated it sitewide, no errors.
Moved (not copied) the bp-themes folder …
Put BP Home theme into themes directory & activated it for the home blog.
Results: none of the links in the My Account dropdown work — all point to
http://blogsite.ca/members/blogname/…
… when our WPMU is set up to have the blog name at the beginning, like:
Modifying the My Account addresses (manually, for testing) to this doesn’t work, either:
http://blogname.blogsite.ca/members/blogname/… OR
http://blogname.blogsite.ca/members/…
That, and the homepage for our site no longer shows a blog page, but a login page — and it doesn’t accept my login & password combo (which worked just fine to get into the Dashboard for my blog).