My panel is being rendered twice

[Jeremy Colton]

I have a panel which has a form.  The corresponding html has a input element
of type 'submit'.  When clicked the form's onsubmit() method is triggered as
expected.  If i have a business logic exception (eg dependent fields were
not completed) then I call the relevant component's error() method.  The
current page is then reloaded.  But my error panel does not display
anything.  Putting breakpoints in my code revealed that my panel's
onBeforeRender() was being called twice!  Ie the page was being rendered
twice!  Once via WebRequestCycle.redirectTo() and once via
PageRequestTarget.respond().

The 1st time around, my form has error messages attached, but the 2nd time
they are null.

Here is my code:

registrationForm = new Form("registrationForm", new
CompoundPropertyModel(resume)) {

            @Override
            protected void onBeforeRender() {
                // TODO Auto-generated method stub
                super.onBeforeRender();
                LOGGER.info("rendering resume panel...");
            }

            @Override
            protected void onSubmit() {
                if (resume.isJob1() || resume.isJob2() || resume.isJob3()) {


                        this.info("thanks for your resume");
                        setResponsePage(BrandedAppHomePage.class);

                        /* need to remember validation errors from this
request so that the 2nd (AJAX)
                         * request can add them back against each component
*/
                        //collectValidationMessages(this);
                        this.error("Please select a suitable file to
upload");

                } else {
                    this.error("Please make a job selection");
                }

            }

            /* called when there's a form validaton error */
            @Override
            protected void onError() {
                LOGGER.warn("in onError...");

            }

        };

        add(registrationForm);
        add(new FeedbackLabel("validation_form", registrationForm));

        job1CheckBox = new CheckBox("job1Choice", new PropertyModel(resume,
"job1"));
        job2CheckBox = new CheckBox("job2Choice", new PropertyModel(resume,
"job2"));
        job3CheckBox = new CheckBox("job3Choice", new PropertyModel(resume,
"job3"));

        registrationForm.add(job1CheckBox);
        registrationForm.add(job2CheckBox);
        registrationForm.add(job3CheckBox);
    }

Could this be somehow facebook-related?  I dont' think the 2nd
PageRequestTarget.respond() should be called.  I don't see it being called
in non-facebook form submits...

Thanks
Jeremy