Adding existing Host to SCVMM: Error 2912

When trying to add an existing Hyper-V-Host to SCVMM I get the following error:

Error (2912)
An internal error has occurred trying to contact an agent on the %serverName%.
(Unknown error (0x80041004))

Recommendation Action
Ensure that the agent is installed and running. Ensure the WS-Management service is installed and running, then restart the agent.

The host used to be managed by SCVMM before without any problems. I removed it and tried to add it to the manager again, because suddenly the status was "Host not responding" for all hosted VMs (even though they're up and running).

The VMAgent and WinRM services on the host are running and restarting them didn't help. A reboot of the SCVMM-Server didn't help either.

A reboot of the VM host is scheduled, let's see if that helps. I keep you posted.

UPDATE

According to MSDN the error code means WBEM_E_PROVIDER_FAILURE ("Provider has failed at some time other than during initialization") in WMI.