An invalid form control with name=[name of textarea here] is not focusable
After researching this, I think the root of the problem is similar to that described here:
Specifically, Silvio's reply on June 17th, 2011, where he says:
There is still this bug in certain case under Google Chrome 12 when having html5 attribute “required” on textarea.
I think this exactly what's happening with my form -- my textarea has an HTML5 required="required" on it, for form validation, but of course, once CKEditor takes over for that textarea, Google Chrome can no longer gain focus for auto-completion, so the form just balks.
Right now, for expediency, I've removed the "required" HTML5 attribute and am relying solely on the server-side to do validation for that field.