[O] Possible bug: Emacs hangs on (require 'org)

[Luke]

I have a strange situation on my laptop.

I'm running Ubuntu 16.04, with Emacs 24.5.1. I'm also using the latest 
development branch from the org-mode git repository (latest changes 
pulled today).

Recently, for some unknown reason, emacs suddenly started to hang on 
startup. Placing some output messages in my .emacs file I was able to 
narrow it down to this line:

    (require 'org)

Loading org-mode hangs Emacs for some reason. If I remove the above line 
from .emacs then Emacs will start as normal (although without org-mode, 
obviously).

I tried creating a minimal-org.el file with the following contents:

    ;; activate debugging
    (setq debug-on-error t
          debug-on-signal nil
          debug-on-quit nil)

    ;; add latest org-mode to load path
    (add-to-list 'load-path (expand-file-name "~/elisp/org-mode/lisp"))
    (add-to-list 'load-path (expand-file-name 
"~/elisp/org-mode/contrib/lisp" t))

And then running:

    $ emacs -Q -l minimal-org.el

...but I still get the same result (Emacs hangs when I run `M-x (require 
'org)`).

Can anyone help tell me what's wrong, or suggest how I try and track 
down the problem?

--
Luke