Go to assignment module > mod_form.php > line 117, there is a typo in the name of a method:

"function validataion"
should be
"function validation"

From what I can tell, subsequent calls to the method use the proper spelling.

(FYI: I'm new to moodle and recently install the 2.0.2 version. In an effort to learn how to create a custom module, I've been pouring through other module code to understand how it operates. A search for this typo returned no results, so my apologies if this was already reported.)