An error occurred while loading either your .emacs file or the system-wide file site-lisp/default.el. Emacs 21.1 and later pops the *Messages* buffer, and puts there some additional information about the error, to provide some hints for debugging.
For information on how to debug your .emacs file, see Debugging a customization file.
It may be the case that you need to load some package first, or use a hook that will be evaluated after the package is loaded. A common case of this is explained in Terminal setup code works after Emacs has begun.