That -196608 error converts to hex FFFD0000. I've seen that sometimes returned to mean "path not found".
If you run the script yourself does it work?
Is it safe to assume that this is an unattended install? If so, try adding "-noninteractive" to PowerShell's parameters.
If the AgentInstall.ps1 script from McAfee? You might try asking them how to go about running it from MDT.