White screen always means some error is occurring. Did you modify any WPMU or BP files? Have you created any custom files?
If so, you could have a space before or after the opening PHP tags. Or, you might have left off something as simple as a semi-colon at the end of a particular line.
There are many possibilities. If you have modified or created your own files recently, then that is where you should first look. If you have installed any new plugins or updated any older plugins (other than BP), then there could be some issue with them. Try disabling them (or moving them out of the way if necessary).
Here’s more info: https://mu.wordpress.org/forums/topic/9045
Hey Jeff, I get what you are saying, but the files are the originals, only running a custom theme.
Thanks Jeff, there was an outdated plugin causing the problems!
Theme files can also cause this issue–although usually you don’t see it WPMU’s backend.
Are you able to login as the Site Admin, or does that also bring up the WSOD (white screen of death)?
I suggest switching to the default BP themes and see if you can login. If you can, then it has something to do with your custom theme–some recent change in the template coding, or possibly a missing custom theme file.
If need be, you can manually change the theme selections in wp_1_options (the options table for the main site blog user) and also in wp_sitemeta. If you go this route, make sure that you first completely backup your database.
Be careful with this procedure as it could lead to more problems. Manually editing data in the backend DB tables is never something you should consider unless you know what you are doing.
Okay, great!
So, disregard my last post. 
Hi Jeff,
Looks like I’m facing the same problem : I can’t login as the Site admin, but the other users have access to their backoffice and see the buddypress Admin bar (meaning Buddypress is active).
I tried to switch to the default BP theme for the home page, but the issue remains.
I don’t know if it has something to do with the issue, but members who register and don’t create a blog are automatically assigned as subscribers on the root blog. This means that there are hundreds of users assigned to this blog. May this be a problem with buddypress ?
Do you see where the problem may come from ?
Thanks in advance for your help
Julien
@Julient
It sounds like a different issue. I assume that you are not getting the WSOD?
If that is the case–that you are not receiving the WSOD–then you should create a new thread as this one is resolved.
I don’t know if it has something to do with the issue, but members who register and don’t create a blog are automatically assigned as subscribers on the root blog. This means that there are hundreds of users assigned to this blog. May this be a problem with buddypress ?
This is normal WPMU behavior. It has nothing to do with BuddyPress.
Ok, that’s what I’ll do !
Thanks
