I'm trying to create a timestamp with both date and time in org-mode (without adding to agenda), and I read from the docs that I should be using this cord:

C-u C-c !

However, I get this in my minibuffer:

screenshot http://zc.d.pr/NxKK/56UjyS0K+

Seems like its waiting for more input. I'm an Emacs n00b so I'm not really sure what's happening here. I get the same behavior with

C-c !

Both versions with . work fine, though:

C-u C-c .

C-c .

What's happening here?

UPDATE: Thanks to suggestions from the comments below, I've determined Flycheck is doing something to screw this up: here's my flycheck config

(use-package flycheck
  :ensure t
  :init (global-flycheck-mode))
(add-hook 'after-init-hook #'global-flycheck-mode)

Where can I look to find if there is a colliding key binding?