distribution .htaccess is the default file that comes with the Joomla! .zip. but I think you already using this so you should try enabling/disabling extension and/or removing the .html suffix alltogether.

Hi Krikor, I resolved the problem, the solution was really strange or at least not obvious to me, however, I put the Cache of the site to OFF under:

Global configuration->System->Cache Settings and put Cache to OFF.

It seems that caching on the site where I'm working (big in size) causes some problems to K2 Archive and K2 Tag Cloud.

For now it seems everything fine, users logged and not logged now can use K2 Archive and K2 Tag Cloud as always.

Thank you for the support.