I have the same problem here. I figured that it will happen when I try to open any subdomain that doesn't exist on my wordpress network.
Lets say I have a.example.com b.example.co and c.example.co set up if I try to access anything.example.com beside those a/b/c I get a white page on the browser and in the Apache's log:
[notice] child pid 18019 exit signal Segmentation fault (11)
That won't happen if I am logged in the backend. I basically don't get any response from apache and I am not sure what to do in order to troubleshoot that... I tried pretty much everything here...
Does anyone have a clue?