Dude, where's my diss? '

Part II, in which I wonder about my copyright

As noted last time, I clearly assert my ownership of copyright on the title page of my dissertation. However UMI also asserts a copyright:

UMI Microform 9840610 Copyright 1998, by UMI Company, All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.

Honestly I don't know what this means. Sounds like they might claim a copyright on the particular microform instantiation of my dissertation, that is, the microfilm, though given the appearance of this text on a pdf, I suspect they may also be claiming a copyright on that particular pdf as well.
Let's see what their website reveals. Off to the support pages and I find this as the second item on a search for "copyright":

No, you do not have to copyright your work unless your school requires you to do so.

Well, mine did, so that seems to rule me out. Since I don't see any other obvious choices, I guess I'll e-mail support and see what they say. Here's my question:

My dissertation cays that I have the copyright, per my university's instructions. The UMI version says that UMI claims a copyright as well, though you also recognize mine. What exactly are the rights that I retain and what are the ones that you hold?
Thanks. 

Two days later (which is actually the first business day after), their reply in its entirety:

You are the copyright owner of your dissertation not us

So that seems good, but I remain a bit suspicious, given their fairly clear claim, so I ask back:

Does that mean I can freely distribute the pdf you made of my dissertation?

This time the reply is:

You would need to call the copyright office to ask them

So I do. The answer from them is that I am free to do what I want with the pdf of the dissertation; that they merely store my work. Awesome.

Next up, where to put the diss for long-term availability.