Error when running Enable-PSRemoting -f

When trying to enable remoting on a local compuetr via Powershell, I get the following error:

> Enable-PSRemoting -f

WinRM already is set up to receive requests on this machine.
<f:WSManFault xmlns:f="http://schemas.microsoft.com/wbem/wsman/1/wsmanfault" Code="2150858909" Machine="FRS.kleerdex.com"><f:Message>WinRM cannot process the request. The following error occured while using Negotiate authentication: An unknown security error occurred.  
 Possible causes are:
  -The user name or password specified are invalid.
  -Kerberos is used when no authentication method and no user name are specified.
  -Kerberos accepts domain user names, but not local user names.
  -The Service Principal Name (SPN) for the remote computer name and port does not exist.
  -The client and remote computers are in different domains and there is no trust between the two domains.

 After checking for the above issues, try the following:
  -Check the Event Viewer for events related to authentication.
  -Change the authentication method; add the destination computer to the WinRM TrustedHosts configuration
setting or use HTTPS transport.
 Note that computers in the TrustedHosts list might not be authenticated.
   -For more information about WinRM configuration, run the following command: winrm help config. </f:Mess
age></f:WSManFault>
At line:50 char:33
+             Set-WSManQuickConfig <<<<  -force
    + CategoryInfo          : InvalidOperation: (:) [Set-WSManQuickConfig], InvalidOperationException
    + FullyQualifiedErrorId : WsManError,Microsoft.WSMan.Management.SetWSManQuickConfigCommand


Any ideas?