Saving a preset prints JSON to screen

Bizarre. I think I've seen this once or twice. Can you try running with Firebug or an equivalent open to see if there are any Javascript errors popping up?

I am having this issue also. Chrome console shows:

Resource interpreted as document but transferred with MIME type text/javascript.

I am dynamically rebuilding a select box using AHAH but this is only done on change. When the form submits (which does not call that function) I get the JSON splat.

The form elements are:

$form['select_platform'] = array(
'#type' => 'select',
'#title' => t('Select platform'),
'#options' => array('N/A' => 'N/A', 'PSP' => 'PSP', 'ps2' => 'Playstation 2', 'ps3' => 'Playstation 3', 'ds' => 'NintendoDS', 'gamecube'=> 'Gamecube', 'wii' => 'Wii', 'xbox' => 'Xbox', '360' => 'Xbox360', 'mac' => 'Mac', 'advance' => 'Gameboy Advance', 'pc' => 'PC'),
'#ahah' => array(
'event' => 'change',
'path' => 'ajax/get_prizes_ahah',
'wrapper' => 'ahah-wrapper',
'method' => 'replace',
),
);

$form['prizes2'] = array(
'#type' => 'select',
'#title' => t('Select from a choice of games'),
'#options' => sr_incentives_get_prizes('game'),
'#prefix' => '

',
);

...and the AHAH method is:

function sr_incentives_ajax_get_prizes_ahah() {

$form_state = array('storage' => NULL, 'submitted' => FALSE);
$form_build_id = $_POST['form_build_id'];
$platform = $_POST['select_platform'];
watchdog('sr_incentives', "PLATFORMAGE: $platform", array(), WATCHDOG_DEBUG);
$form = form_get_cache($form_build_id, $form_state);

$args = $form['#parameters'];
$form_id = array_shift($args);
$form_state['post'] = $form['#post'] = $_POST;
$form['#programmed'] = $form['#redirect'] = FALSE;

$query_prizes = db_query("SELECT disp, name FROM {sr_incentives_prizes} WHERE category = 'game' AND count > 0 AND platform = '%s' ORDER BY disp ASC", array($platform));
$prizes = array();
while ($row = db_fetch_array($query_prizes)) {
$prizes[$row['name']] = $row[disp];
}

$ahah_form = $form['prizes2'];
$ahah_form['#options'] = $prizes;

form_set_cache($form_build_id, $form, $form_state);

drupal_process_form($form_id, $form, $form_state);

$form = drupal_rebuild_form($form_id, $form_state, $args, $form_build_id);

unset($ahah_form['#prefix'], $ahah_form['#suffix']);

$output = drupal_render($ahah_form);

drupal_to_js(array('status' => TRUE, 'data' => $output));
}

buddhamagnet: can you test taking out the custom code and seeing whether the issue persists?

Any luck trying this without the custom code? If the form is not getting rebound by jQuery after something is done to it, this will be the result.

Closing, please reopen if the issue is persisting or you can give more information.