When testing DAV resource with ownCloud I was left with a ghost entry of an agent. I had manually configured a CardDAV agent and after deleting it, it is still listed in Kontact Contacts and in the Browser tab of akonadiconsole. It isn't listed in the agent list.
In akonadiconsoles Browser tab the "Delete folder" entry in the context menu is grayed out, and when I select "Delete Address Book" From Kontact the following is displayed in .xsession-errors and nothing else happens:

void AgentManager::removeAgentInstance(const QString&) Agent instance with identifier "" does not exist

The Attributes tab of folder properties says:
ENTITYDISPLAY: ("OC Contacts" "folder-remote" "" ())
AccessRights: WCD

The Internals tab shows 
Identifier 76
Remote identifier akonadi_davgroupware_resource_74
Content types: inode/directory; text/directory

When selecting "Dump to XML..." and select a file name, the following is written:
"Cannot connect to agent instance with identifier 'akonadi_davgroupware_resource_74', error message: 'Could not get owner of name 'org.freedesktop.Akonadi.Resource.akonadi_davgroupware_resource_74': no such name'"


Reproducible: Didn't try

Actual Results:  
The agent can't be fully deleted

Expected Results:  
The AgentManager should remove all parts of the agent.

KDE 4.10.2