I recently upgraded my K2 to version 2.6.5 and I figure out when I'm not login the K2 Tag menu does not work property, all of the menu tags result same content, this should be related to cache system because while I'm loged in to the system, everything work correctly.

please examples:

zoomit.ir/ces
zoomit.ir/microsoft
zoomit.ir/apple
zoomit.ir/ces-2012
zoomit.ir/android
zoomit.ir/android-guide
....
do you have a quick fix or I should roll back to oldest version.

Thank you in advance for your prompt reply.

I found the same problem in K2 Demo version on demo.getk2.org:

demo.getk2.org/show/tag/extension

demo.getk2.org/show/tag/joomla

demo.getk2.org/show/tag/Australia

Bugs should be reported in the bug tracker as the two K2 devs doesn't care about the support forum.
Although I doubt you will get a respond there.

turn joomla's cache off

I have reported this problem:

code.google.com/p/getk2/issues/detail?id=478&colspec=ID%20Type%20Status%20Priority%20Owner%20Summary%20Opened

It's exactly the same problem for me and I think taht it happens since K2 v2.6.3. if you visit:

www.madridout.es/sucesos/itemlist/tag/policia

www.madridout.es/sucesos/itemlist/tag/maltrato

Yo will find the same items. Also, I think turning off joomla cache it's not the solution.

after the update I have also some problems with my side.
What can we do?

I have re-installed K2 2.6.2 and the problem has gone. I will wait until this is fixed to install new versions because in my web I really have many thing working with tags.

I have the same problem too... ( Installed versions Joomla 2.5.9 + K2 2.6.5)

As I said in a previous post i had to re-install K2 2.6.2 in order to use cache and tag views properly.
However, I have found a hack/solution with K2 2.6.2 that let me use anyk2link. This is a new feature implented in k2.6.5 that allows you to create a generic menu to all the categories, tags, autors that don´t have it to avoid duplicate urls. In older version google robot used to found urls like:

• misite.com/menu1/itemlist/tag/firsttag
• misite.com/menu2/itemlist/tag/firsttag
• misite.com/menu3/itemlist/tag/firsttag

This is considered duplicate content by google webmaster tools. Whith anyk2link this disappears because you create a menu linked to no category that works like a generic menu. For example, I have created a menu called "i" and you can see that all tags are misite.com/i/itemlist/tag/firsttag (it's a unique url).

To allow that without install 2.6.5 (because 2.6.5 doesn´t works fine with cache and K2 tags view) I tested to replace /components/com_k2/ helpers/route.php of 2.6.2 version with the one in 2.6.5 and it works!

Maybe this could help someone

In my sites with K2 2.6.5 I fixed it with some modifications in
components/com_k2/controllers/itemlist.php

Se changes here:

github.com/creativeprogramming/montebianco/commit/f52153d8102b6edbe5b20feb57cf59ec5fe21a3e