JDE key bindings

Hello,

I am just trying to teach jde some keybindings.  For example, I want to bind 
something to C-c C-t C-c. Now I get an error message "Invalid prefix 
character" because some function I don't even know was bound to C-c C-t 
previously. 

In a lisp file, I would bind C-c C-t to nil before and everything would be ok.  
But if I try to do so, the customization buffer of jde says that nil is an 
invalid function. 

So question: How should I handle that situation? Is there a clean way to do 
the customization of the key-bindings of jde outside that customization 
buffer, directly in a file? If I try to evaluate code like shown below, I get 
a quite long error message I don't  understand, although evaluating the 
define-key lines alone works:

(add-hook 'jde-mode-hook
		  '(lambda ()
			 (define-key jde-mode-map [?\C-c ?\C-t] nil)
			 (define-key jde-mode-map [?\C-c ?\C-t ?\C-c] 'jde-gen-class-buffer)
))

Thanks for hints,

Wolfgang