After spending hours checking your issue, this issue doesn't seem to be related to EasyDiscuss. Earlier you probably created a new user group with the id "16" and you configured Joomla to use this new user group. Somehow this group got deleted but you did not change this in the user options again for the default public group.

I have re-saved the settings under Joomla Users -> Options and it works fine now.

I am sorry for your time spent, I really appreciate it a lot!

I just can't understand why subcategories of one category are dublicated (showing twice), but another subcategories of other category are still not showing up. I have attached a picture. And I added new subcategory - its not showing up, when I want to post. This situation is now the same for all (guests, registered and super user). Thank you very much if you could look at it.

Hi Dalia,

I am really sorry for the delay of this reply as I was going through all the codes in order to found the issue. After some time of checking, it seems like there are some sort of custom code inside /components/com_easydiscuss/helpers/helper.php as you can see here, http://screencast.com/t/wLxerO3u6 . When I remove it everything is displaying correctly now, http://screencast.com/t/n7w06aCcg1jK .