I definitely feel like it's something in PowerCLI 6.5, but it's very inconsistent. Like if I grabbed events for a vm object, it would return fine. If I grabbed all my $vmhosts and did a get-vievent, 1 or more may error out w/ deserialization errors. when I try to hit individually, some will work some won't.
The one consistent thing is that 6.0R3 doesn't exhibit these issues at all.
(I've been using a Fusion Windows 7 VM and keep snapping back to 6.0R3)