I haven't used ajaxform, but I think this means that you can do
something like this:
$("#myForm").bind("form-pre-serialize", function() {
// put the data from the editor back into the form.
});
How to actually get the necessary data from CK you'll have to look at
the CK editor's documentation. There should be a simple function to
synchronize back with your textarea, but if not, there should still be
a call to get the rich data as a string which you could then manually
insert into your text area.
Alternately, there are some jQuery wrapper plug-ins for the rich
editors. I've never used them, but they may be easier to use than
your manual integration:
http://www.google.com/search?q=jquery+ckeditor+plugin
Good luck,
-- Scott
P.S. Unbelieveable! Google was rejecting my post from it online
interface when I used the name of the editor. What I'm calling
"CKEditor" here had in the post an initial "F" as well.