Completion stopped working

[Thorsten Jolitz <tjolitz@gmail.com>]

Hi List, 

recently auto-completion stopped working completely for me, and I'm
trying to chase the root of this problem. 

Therefore I have 2 questions (at the moment):

1. C-h f and C-h v

With 'emacs -Q', these commands with point on a function or variable
(still) propose the symbol at point as a default, e.g.

,------------------------------------
| Describe function (default defvar):
`------------------------------------

but this stopped working when I load my .emacs. "Who" is in charge of
showing this default value?

2. auto-complete popup window

I remember in the back of my head that I disabled a (generic) option to
popup help windows or so - but I don't remember the name of this option
anymore and thus don't find it in my .emacs.

Does such an option exist and whats its name?
Could this be the reason that auto-complete-mode stopped working?

PS 1
System-info:

,----------------------------------------------------------------
| GNU Emacs 24.3.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.6.4)
|  of 2013-03-18 on eric
| Org 8.0-pre
| Ma Gnus v0.2
`----------------------------------------------------------------

PS 2
my (simple) auto-complete-mode config which used to work:

,---------------------------------------------------------------------------
| ;; **** 26.8.4 Auto Complete Mode
| 
| ;; auto-complete-mode
| (when (require 'auto-complete nil 'NOERROR)
| 
| (add-to-list 'ac-dictionary-directories "~/.emacs.d/dict")
| (require 'auto-complete-config)
| (ac-config-default)
| 
| ;; more add-hook's in other places, e.g. for emacs lisp
| (add-hook 'LaTex-mode-hook lambda () (auto-complete-mode +1)))
| (add-hook 'org-mode-hook (lambda () (auto-complete-mode +1)))
| 
| ;; (define-key ac-menu-map "\C-n" 'ac-next)
| ;; (define-key ac-menu-map "\C-p" 'ac-previous)
| 
| (setq ac-auto-start 3)
| 
| (define-key ac-complete-mode-map "\M-/" 'ac-stop) )
| 
| ;; (define-key ac-complete-mode-map [f12] 'ac-complete)
| ;; (define-key ac-complete-mode-map "\r" nil))
`---------------------------------------------------------------------------

-- 
cheers,
Thorsten