I have noticed that CCMeval is failing on my Windows 8/ Windows Server 2012 clients and the WMI repository is being reset all the time.
This is because you have installed the ConfigMgr 2012 RTM Client on these operating systems.
Microsoft added some new WMI classes to every namespace in Windows 8/ Windows Server 2012 in order to support the WMIv2 infrastructure. As the ConfigMgr 2012 RTM version of the Client Health Component (CCMeval), is not aware of these new classes it can fail to remediate them, leading to potential corruption and the WMI repository being reset each time CCMeval runs.
Microsoft strongly recommends you DON’T install the RTM version of the ConfigMgr 2012 Client on these OSs, but wait until Service Pack 1 is officially launched (early 2013), which will provide full support for these OSs.