Re: 404 errors turning into 500 errors through internal redirects
You’ve just got to tear out *everything*. All this domain mapping and other things. Get down to a bare install of bp 1.0 using the default themes and wpmu 2.7.1.
Did you remove your previous bp install from /mu-plugins? Why is it trying to get to an avatar image from there? I suspect it’s all your *other* addons in some combination with the upgrade to 2.7.1 from 1.x and the addition of bp into the mix that is causing your problems.
Take things back to a known, working state. Start with bare 1.x. Then upgrade to wpmu 2.7.1 incrementally. From everything I hear on the wpmu forums this is the recommended procedure. Jumping from 1.x to the latest version in one step isn’t recommended.
When wpmu 2.7.1 is operating correctly without any fancy domain mapping installed. Then install bp 1.0 and get that working. Gradually add in your other plugins and test before moving to the next one. That procedure, by itself, may solve your problems.
The upgrade and installation of new features procedure, that you have been practicing currently, has driven your site insane. You are trying to track down individual symptoms of a completely unknown state of affairs. You’ll just wind up chasing symptoms instead of curing what’s wrong.