Oil in the coolant

[P. A.]

OK guys, what ways, other than a bad head gasket, can oil get into the
coolant system? I have the UrS metal head gasket on the car (installed at
last timing belt job) which is fairly bullet proof from what I hear from the
UrS guys. But I've got oil floating in my coolant reservoir and am trying to
think of all the other ways that oil can get into the system. Could a bad
seal/bearing in the turbo allow it's cooling water to get into the oil?
Thanks for any ideas of what else to consider before I pull the head.
Patrick