The Joomla! open portal extension needs a slight modification to be compatible with Joomla! 3.4.x
In the file /administrator/components/com_advancedopenportal/controller.php around line 18 needs this:
function display($cachable = false)
to be changed to this:
function display($cachable = false, $urlparams = false)
Hope this helps someone. If I find anything else, I just installed it and haven’t test driven it very far yet, I’ll post it here.