The agent log is most often merely a bookmark to the actual detail.
You should look to the local machine to see if there is more detail in the mcscript.log at the time, and also if the VirusScan installer has actually launched in which case it may have it's own logging running that can be investigated.
i'd suggest you also validate a completely local installation of VirusScan outside of ePO is successful or not.
Is your task in the EPO configured properly? Ensure "Product Deployment" is selected, then in the next screen "VSE 8.8, Install, Current".