When upgrading to 8.5, I have noticed that some machines are reporting back to ePO as having both 8.0 and 8.5 installed. When this happens, 8.5 refuses to update.
I have tried removing all versions of VirusScan (via ePO) and reinstalling the agent (again via ePO) but it still 'hangs onto' 8.0. The only way to get rid of everything is for someone to physically go to the machine, uninstall the agent, then delete any references to McAfee and Network Associates from C:\Program Files and the registry.
We have seen this happen occasionally when using EPO to upgrade systems to VSE 8.5i. It is a pain for us since we have to send out a technician to fix the broken upgrade.
The best way that I have to keep the number of failed upgrades is to have EPO do a deployment task to uninstall VSE 8.0i and then install VSE 8.5i. I have read somewhere on this forum that if you do an upgrade then you might see more failed installations.
I have so far got about 1/2 my systems on VSE 8.5i and the others on VSE 8.0i. We are going to try to get the rest of the systems running VSE 8.0i after the holidays.