Symptoms

The following error is presented when going to a particular list on a site where the K2 for SharePoint 2010 features are activated and clicking the K2 Wofklow button the list/library ribbon:

Server Error in '/' Application.
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Runtime Error
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.

 

Diagnoses

After disabling the custom error settings in the web.config in this case, the error eluded to the WebDesigner virtual directory being a problem. This particular environment had 2 web front ends, and the WebDesigner virtual directory was only enabled as an application on one of them. This WebDesigner virtual directory can be found in on the SharePoint Web Front End in IIS>tsite where site collection is hosted]>layouts>WebDesigner.

 

Resolution

In this case, the error mentioned in the symptom was presented on a list that existed at the subsite level of the site collection.

After double checking that the WebDesigner Virtual Directory was actually set as an application in IIS under the site where the site collection was running on both SharePoint Web Front Ends, the following was performed to resolve the issue:

A re-activation of the K2 Designer for SharePoint features on the subsite and an activation of the K2 Features on the topsite did the trick--

To register the components on the topsite
1. Open Central Administration
2. Go to "K2 for SharePoint" from the quicklaunch on the left
3. Go to "Activate All K2 Features and K2 Configuration Settings
4. In the yellow dropdown, make sure the topsite site collection is chosen.
5. Default settings here should be ok
6. Click OK at the bottom. This will then go through the activation. The activation will recycle the application pools on the web front end
7. After the activation has completed, go to the root site home page, go to Site Actions in the upper left, and double check that the "K2 Site Settings" link is there at the bottom of the Site Actions menu. This indicates that K2 has been activated on the site collection.

To update the K2 Designer features on the subsite level:
1. Open Central Administration
2. Go to "K2 for SharePoint" from the quicklaunch on the left
3. Under "Settings" Choose "Activate K2 Designer for SharePoint Features"
4. In the upper right of the page, choose the Intranet/ops subsite
5. Default settings should be ok
6. Click OK
7. Go back to subsite/list where you were originally seeing the server error and see that you are able to access the K2 Workflow for the list.