After reading all the wonderful comments from desperate people having issue, I got my hopes up again..But unfortunately the problem still exists.. I just migrated a site to Joomla 2.5, using the Joostrap basic template (responsive). K2 is essential for my client, however I cannot get frontend editing working. The Save and Cancel buttons will not close the modal popup. I know it's a template issue as K2 frontend editing works okay in the atomic template.
Any ideas how to solve this issue?????

Tnx for your reply. Meanwhile found out some more specific things:
In this case the template is a Joostrap template. This template removes all Mootools code in the template unless it is overridden for certain menu items..

* ==================================================
* Disable mootools-more except for selected itemids to solve bootstrap conflicts
* ==================================================
*/
$enabledItemids = array();
$enabledMootoolsString = $this->params->get('mootoolsItemids', '');
$editingMootools = $this->params->get('editingMootools', 1);

// Decode the enabled Itemids array
if ($enabledMootoolsString != '')
{
$enabledItemids = explode(',', $enabledMootoolsString);
}

if ($editingMootools && ($option != 'com_content' || $view != 'form' || $layout != 'edit'))
{
$editingMootools = 0;
}

// If the itemId isn't in items that need mootools disable mootools
if (!$editingMootools && (empty($enabledItemids) || empty($itemId) || !in_array($itemId, $enabledItemids)))
{
// Disable mootools javascript
unset($doc->_scripts[$this->baseurl . '/media/system/js/mootools-core.js']);
unset($doc->_scripts[$this->baseurl . '/media/system/js/mootools-more.js']);
unset($doc->_scripts[$this->baseurl . '/media/system/js/core.js']);
unset($doc->_scripts[$this->baseurl . '/media/system/js/caption.js']);
unset($doc->_scripts[$this->baseurl . '/media/system/js/modal.js']);
unset($doc->_scripts[$this->baseurl . '/media/system/js/mootools.js']);
unset($doc->_scripts[$this->baseurl . '/plugins/system/mtupgrade/mootools.js']);

// Disable css stylesheets
// unset($doc->_styleSheets[$this->baseurl . '/media/system/css/modal.css']);
}

---

the only way i could get the k2 editing popup working properly was to uncomment this whole part in the template code, so avoiding to not load mootools .. as all pages have to be editable from the frontend, so assigning all itemid's does not make sense..

not the best solution i guess, but had to get on with it....

site url www.nvrb.nl/nvrb25