Question Preview and auto return to the topic

Kunena.com has K1.0.10 Build 1344, which is the same as in download area.

What is your php version? Does downgrading to 1.0.9 fix it? Can you provide me URL to your site?

My version of Kunena is 1.0.10 Build 1344.
I have returned to the Kunena 1.0.9 and preview and auto return began to work.
I use a local server.
It works on a platform of program Denver3 ( www.denwer.ru ).
It includes: Apache 2 + SSL, PHP 5, MySQL 5, phpMyAdmin. Also I have instaled addition ( www.denwer.ru/packages/php5.html )
and has included in PHP php_mdstring.dll

There are system information from Joomla:

PHP Built on: Windows NT 5.1 build 2600
Database Version: 5.0.45-community-nt
Database Collation: utf8_general_ci
PHP Version: 5.2.4
Web Server: Apache/2.2.4 (Win32) mod_ssl/2.2.4 OpenSSL/0.9.8d PHP/5.2.4
Web Server to PHP interface: apache2handler
Joomla! Version: Joomla! 1.5.10 Production/Stable [ Wohmamni ] 27-March-2009 23:00 GMT
User Agent: Opera/9.64 (Windows NT 5.1; U; uk) Presto/2.1.1

I concur with imperium. I, too, have experienced the same non-autoreturn to forum after posting a message.
Kunena v1.0.10_stable_b1344_2009-05-21

Similar information (older version of Joomla, though):

PHP Built on: Windows NT 5.1 build 2600
Database Version: 5.0.51b-community-nt
Database Collation: utf8_general_ci
PHP Version: 5.2.6
Web Server: Apache/2.2.9 (Win32) DAV/2 mod_ssl/2.2.9 OpenSSL/0.9.8h mod_autoindex_color PHP/5.2.6
Web Server to PHP interface: apache2handler
Joomla! Version: Joomla! 1.5.7 Production/Stable [ Wovusani ] 9-September-2008 23:00 GMT
User Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.648; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)

The Preview button is non-effective.

Hmm.. Do you have any sef component installed?

I have to say, that I don't have any idea why they are not working. Do they work in here or with FireFox3?

I have created a new database with utf8_unicode_ci.
Also has created new site Joomla and instaled Kunena 1.0.10.
Preview and auto return to the topic are works.

This means that there is/was something wrong in your installation. What it might have been -- I have no idea. I believe that it was some setting in Joomla or Kunena which was causing this.