Error "Key sequence starts with non-prefix key"

[Thorsten Jolitz <tjolitz@gmail.com>]

Hi List, 

with the following expression defining key-bindings (assume
outline-minor-mode-prefix is C-c):

(let ((map (lookup-key outline-minor-mode-map outline-minor-mode-prefix)))
  (define-key map "\C-a" 'show-all)
  (define-key map "\C-\M-l" 'outshine-insert-all-links)
  (define-key map (kbd "C-v C-a") 'outshine-babel-sha1-hash) [...]

I get an error because of the last line (no matter if I use the `kdb'
macro or just write "\C-v\C-a"):

Debugger entered--Lisp error:
(error "Key sequence C-v C-a starts with non-prefix key C-v")

I wonder what I have to do to declare e.g. C-v or C-x as prefixes for
submaps to let me define bindings like 'C-c C-v C-a', i.e. (define-key
map (kbd "C-v C-a") ...) with C-c prefix? 

Maybe its simple and RTFM applies, but I couldn't find it ...

-- 
cheers,
Thorsten