Unbalanced parentheses will cause errors in elisp files when they are loaded.
As of GNU Emacs 21.1, the command
‘check-parens’ checks for unbalanced parentheses automagically. Without it, use C-M-f and C-M-b across [[Sexps?]]. These include balanced parentheses, so when it fails, you know you have reached the problematic spot.
If you’re editing emacs-lisp code, why not turn on check-parens on a save? Here’s the highly uncustomizable code to do it. Note that it will not let you save until you correct the error, which maybe not good for your situation.
; could be bad, will not let you save at all, until you correct the error (add-hook 'emacs-lisp-mode-hook (function (lambda () (add-hook 'local-write-file-hooks 'check-parens))))