I have attached the install log for a New install of Symantec.
Attachment(s)
Please follow this document
http://www.symantec.com/business/support/index?page=content&id=TECH217284
The issue is not a Root Certificate issue. After remotely connecting to a affected system I copied the install package directly on the system and started the install. install completed without a issue. the package that I used on the system directly is the same as the package used from the SEPM. can you review the log i provided again to see if there are other issues.
Thanks
The actually thing i observerd from the log you attached is that downgrade failed and also the RORU process wasn't successfull due to permission issues ,
Enable Windows Installer Debugging - Please refer Microsoft KB for Instructions on how to enable this -http://support.microsoft.com/kb/223300
Attach the windows Installer log