I remember getting this error a coupe of years ago as well, can't remember how it got fixed though.
I cannot create new users, no matter what I do, I get: Error
The form submission is incomplete. Perhaps the form size exceeds configured server or browser limits.
post_max_size = 2000M so that cannot be the problem.
max_input_vars = 1000
max_input_nesting_level = 64
I also tried lowering the allowed users on a page to 2.
I only want to allow a second user, that's it
It is a clean installation on a brand new Ubuntu 14.04 / Apache 2.4 PHP 5.5. Everything works like a charm except adding users.
I pulled a user from my old database (14.07) and imported it in the new one (14.11) but that doesn' work either. Wishful thinking?
Any ideas? A workaround?