[Users] Problem with host

Hello All, I was a little bit to enthusiastic and removed a Test-Datacenter with 1 test cluster and 1 host in it. Now I have these error messages (but the host doesn't exist anymore) : Host apollo01 became non responsive. It has no power management configured. Please check the host status, manually reboot it, and click "Confirm Host Has Been Rebooted" Alerts (2) Events Tasks (0) 2013-Nov-19, 10:37 Host apollo01 became non responsive. It has no power management configured. Please check the host status, manually reboot it, and click "Confirm Host Has Been Rebooted" And on top of that, I can't re-add the host, because oVirt still things he is present.. Anybody knows a solution to this issue? Kind Regards, Koen