C-h k C-c b to show what command is being run. Click/press space on the .el link in the first paragraph to see the code.
(global-unset-key "\C-cb") in your .emacs to unset the key.
First find what command is being run with that keypress with
C-h k C-c B. If emacs reports
C-c B is undefined It's probably falling back to the lowercase command,
In the case of a fallback like this, binding a capital key with
(global-set-key (kbd "C-c B") 'command) will leave the fallback key in place.
*help* window that describe-key brings up will mention an
.el file in the first paragraph, you can bring it up with a click, or space when the point is on it. Your command will likely be being set somewhere in that code.
To find the code try searching for
set-key, some variations of your
kbd string, or if worst comes to worst,