Settings ==> Linktocontent gets me an error when I select "Category"

The default is activated.
Beneath that I have furthermore the choice of selecting:
-categories
-taxonomy
-taxonomy content

Ok, this is not the latest version (should include "forum" as well). But that doesn't matter.

I would like to enable the categories.
If I do so, my drupal gets me the error-message:
"Validation error, please try again. If this error persists, please contact the site administrator."

Hm. I never saw this message before.
Which drupal version do you use?
Perhaps 4.7.4?

Ah, I got it: v4.7.4 requires a new form-tag ("form_token"). If it is not present, validation will fail.
I'll will fix this.

Thanks for your feedback.

Updated linktocontent.module as descriped in the converting guide.

I suggest you download the latest package and replace linktocontent.module (v1.8) with the newest version (v1.9; see above) if it isn't already in.

Please reply if it is working.

But no nodes are shown.
Do you have selected some node types in the node-type-fieldset?

Ok, lets try something.
Guess you have the following structure:

+ vocabulary #11 (vid: 62; no nodes)
  - term #13 (tid: 63; has some nodes)
    - term #16 (tid: 64)
  - term #9

Please got to "http://[your_drupal_path]/?q=ltc/linktonode/".
There you should see something like this:

{ 
   "category": [ { "vid": "62", "tid": "62", "title": "vocabulary #11" } ], 
   "node": { } 
}

Then enter "http://[your_drupal_path]/?q=ltc/linktonode/62" (replace the number by the displayed "vid").
You should see something similar:

{ 
  "category": [ { "vid": "62", "tid": "63", "title": "term #13" }, 
                { "vid": "62", "tid": "68", "title": "term #9" } ], 
  "node": { } 
}

Result of "http://[your_drupal_path]/?q=ltc/linktonode/62/63":

{ 
  "category": [ { "vid": "62", "tid": "64", "title": "term #16" } ], 
  "node": { "node/48": { "nid": "48", 
                         "title": "node #48 (page)", 
                         "date": "2006-09-01 18:27", 
                         "author": "", 
                         "type": "page", 
                         "href": "/node/48", 
                         "orig_href": "node/48" 
                        } 
               } 
}

(To go to a deeper level just replace the last number by the terms tid.)

If you see some nodes in the results (try to take a vocabulary where you've got a story/page in one of the first terms) everything works fine.
I assume your browser uses a cached version of the javascript files. Please call them (unctions.js, dropdown.js, nodelist.js) directly in your browser and try again to call the plugin.

Hopefully it will work now.

Hm, tricky. "category": false tells, that there are no sub-categories.
I've created two screenshots:
with and without "container" and "category" enabled as content type.
Could you please check if you get similar results in the plugins node listing.

So, if I enable the types Container and Category they do show up when I create a new linktonode as is shown in your first screenshot.
Sounds good.

In your second screenshot I see the nodes that are not in categories or containers, right?
Ähm, not really. The dropdown shows the two sub-categories of "vocabulary #11".
Because no nodes are stored in "vocabulary #11" the node list is empty.
In the first screenshot the two categories are listed (because you've checked the type "category" in settings").
If their are nodes in the category (see screenshot) they are listed additionally to the categories (highlighted).

I think i dont see what is wrong (stehe auf dem Schlauch...).
Ich auch ;-)
[By the way, do you have skype or something similar, then we can talk faster and nail down this pronlem (you could mail me).
I am away for the next 6 hours so we can proceed tomorrow.]

If I understand you module right, i should see in that case all the nodes that are in the Container "Links" and in the Category "Links to Multimedia".
Right.

I'm so sorry that you have to struggle with me.
No problem. I would have wondered if there where no more problems.

"Your module gives me the ability to link to EVERY node that I have created within my Drupal. They dont need to be inside a container or category"
Unfortunately: false.
You will only see nodes that are "stored" inside a container/category and which type is one of the selected.
I will change the module so that nodes that do not belong to a container are listed on "the first page".
For other types (for example: event; I do not now know whether events are listed or not) I will add an extension from time to time.

I'm back again.
Please skype ("st._.borchert" without both dots) or contact me so we can fix the problem.

I added a patch to display uncategorized nodes in the "first" listing.
Do you have a positive result?

Nice to hear.
I will commit the patched file.

linktonode_default.inc