Have you tried deactivating all plugins and switching to the twentythirteen theme to start finding what’s causing that error? If that fixes the error, reverse your steps one by one to find the problematic one.
I tried switching themes and returning to default permalinks. So far it’s no go. I’ve tried flipping off all plug ins but the security plug ins. Does anyone know if wp better security or wordfence would cause this? I’m using them on another site that was also updated and they are having no trouble there.
What is the error you are seeing?
I’d suggest deactivating ALL plugins and switching to a default theme with them all off.