missing wbem files

I began having errors that pointed to a corrupt WBEM\repository folder. I tried stopping and starting the windows management instrumentation service, but it was already stopped and wouldn't start. I discovered that there were no files in the wbem folder. I copied the entire wbem folder from a working machine and rebuilt the repository folder by stopping WMI, deleting repository files, starting WMI, and rebooting. Norton AV was still having problems so I uninstalled and re-installed, updated definitions, and performed a full scan. It found no errors. Computer ran fine for several months, but now it won't boot. I am assuming that it has the same problem again. What would be the root cause of my missing wbem files? I found another thread that suggested the user deleted them unintentionally, but I'm sure that is not the case with this one. Is there malware that would cause this, or could my AV be causing this?