Solved Getting com-kunena-trash-manager in my SEF URL for the blog

Like I said, your Joomla menu table is corrupted. It has nothing to do with Kunena -- I've seen this happening a few times and there's nothing you can do from Kunena.

But in Joomla there's a button that tries to fix this...

It has actually to do with Kunena
I retraced the error - It is caused be erroneous creation of administrator menu during kunena installation.
During the creation of it's menu - Kunena somehow managed to make an error in menu item's children range.
You can see this error in table menu, in my case in com-kunena-trash-manager position.
I saw that the com-kunena-trash-manager had in column "lft" value 134 and "rgt" 370
This caused that all new menu items with value between 134 and 370 were thought by joomla to be trash manager's children menu items and thus trash manager's link alias was made to be in their paths.

In my version (2.0.2) the trash manager doesn't have any children menu items, thus such range of values should never occur.

To fix this issue one must first fix this value for trash manager and any other menus of which you are sure that they shouldn't have any children (the range for elements with no children should be for example lft="126" and rgt="127",thus rgt should be lft+1 ), and then in the same table, delete "com-kunena-trashmanager" from all the paths in the same table. You don't have to recreate all the menus.

I do not know how to contact Kunena team, or wether this error is fixed in current version, but just this is the solution to the problem I found.

Kogi wrote: In my version (2.0.2) the trash manager doesn't have any children menu items, thus such range of values should never occur.

Are you discussing a problem with K 3.0.4 or with K 2.0.2?

The error, as I wrote - is created during installation.

Thus it may exist even after updating.

I am writing what I found out.
It may be helpful for those that still experience this problem, I don't think that there might exist any other reason for this problem to occur.

What version of Kunena are we discussing?

sozzled wrote:

Kogi wrote: In my version (2.0.2) the trash manager doesn't have any children menu items, thus such range of values should never occur.

Are you discussing a problem with K 3.0.4 or with K 2.0.2?

Did the error occur during installation or did the error occur after installation? In either case, please watch the video vimeo.com/69818669 .

As Matias wrote, reason for the problem is that the Joomla menu table became corrupted. How it became corrupted is a mystery. Depending on your version of Joomla, there is a button to fix this.

I am a programmer myself.

From the looks of it - this error will not show itself immediately - it doesn't change any existing menus, and will only start changing paths to menus created after kunena installation.

I've just made another test installation of joomla, the same version as I used earlier, and installed kunena in it, also the same 2.0.2 version, but the error didn't occur again.

So maybe You are correct, it might be joomla error made because the joomla creators don't know that SQL supports recursive queries and they don't have to make use such complicated methods to indicate who is whose parent and child, or it might be caused by my quite complex menu that I had just before kunena installation (but I didn't have such complex menu in the test I just made).

The menu's structure is handled by quite complicated functions, thus there might be a hidden error there (though isn't it strange that it keeps repeating itself specifically with kunena's trash manager??).

As for configuration report - it doesn't exist in my kunena version, so I cannot attach it.