Would it be possible to attach the agent install logs so I can have a look? (Somewhere in the %temp% folder structure will be a McAfeeLogs folder - if you could zip and attach that it would be great.)
As you point out there's a lot of new stuff in MA5, including the self-protection functions which in theory could require a reboot: I'm a little surprised you've seen a lot of these, though...
Thanks -
Joe